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VIEW OF BECKER CONTINUOUS MILLER MILLING CONNECTING-ROD FIXTURE 

Courtesy of Becker Milling Machine Company, Hyde Park, Massachusetts 




Modern 

• * 

Shop Practice 


A General Reference Work on 

MACHINE SHOP PRACTICE AND MANAGEMENT, PRODUCTION MANUFACTURING, 
METALLURGY, WELDING, TOOL MAKING, TOOL DESIGN, DIE MAKING 
AND METAL STAMPING, FOUNDRY WORK, FORGING, PATTERN 
MAKING, MECHANICAL AND MACHINE DRAWING, ETC. 


Editor An- Chief 

HOWARD MONROE RAYMOND, B. S. 

Dean of Engineering, Armour Institute of Technology 


Assisted by a Corps of 

MECHANICAL ENGINEERS, DESIGNERS, AND SPECIALISTS IN SHOP METHODS 

AND MANAGEMENT 


Illustrated with over Two ‘Thousand Engravings 


SIX VOLUMES 



CHICAGO 

AMERICAN TECHNICAL SOCIETY 

1916 




I J 1160 

■ lie 


Copyright, 1902, 1903, 1904, 1906, 1909, 1913, 1916 
BY 

AMERICAN TECHNICAL SOCIETY 

Copyrighted in Great Britain 
All Rights Reserved 



DEC -4 1916 


©CI.A445943 



Editor-in- Chief 

HOWARD MONROE RAYMOND, B. S. 

Dean of Engineering, Armour Institute of Technology 


Authors and Collaborators 


EDWARD R. MARKHAM 

Instructor in Shop Work, Harvard University and Rindge Technical School 
Consulting Expert in Heat Treatment of Steel 
Formerly Superintendent, Waltham Watch Tool Company 
American Society of Mechanical Engineers 

V* 


CHARLES L. GRIFFIN, S. B. 

Assistant Engineer, The Solvay-Process Company 
American Society of Mechanical Engineers 


HOWARD P. FAIRFIELD 

Assistant Professor of Machine Construction, Worcester Polytechnic Institute 
American Society of Mechanical Engineers 

V 


JOHN LORD BACON 

Consulting Engineer 

Formerly Instructor in Forge Work, Lewis Institute, and Instructor in Shop Work, 
University of Chicago 
American Society of Mechanical Engineers 
Author of “ Forge Practice ” 




BENJAMIN B. FREUD, B. S. 

Associate Professor of Organic Chemistry, Armour Institute of Technology 
Member, American Chemical Society 
Member, American Electrochemical Society 


ERVIN KENISON, S. B. 

Associate Professor of Drawing and Descriptive Geometry, Massachusetts Institute of 
Technology 


GEORGE W. CRAVENS 

Mechanical and Electrical Engineer 

Sales Manager, C and C Electric and Manufacturing Company 




Authors and Collaborators—Continued 


H. B. PULSIFER, S. B., Ch. E. 

Assistant Professor of Metallurgy, Armour Institute of Technology 

Member, American Chemical Society 

Member, American Institute of Mining Engineers 




FRANK E. SHAILOR 

Mechanical Engineer 

General Manager, Detroit Welding and Manufacturing Company 




GLENN M. HOBBS, Ph. D. 

Secretary and Educational Director, American School of Correspondence 
Formerly Instructor in Physics, University of Chicago 
American Physical Society 




WALTER W. MONROE 

Instructor in Pattern Making, Worcester Polytechnic Institute 


FREDERICK W. TURNER 

Head, Department of Pattern Making, Mechanic Arts High School, Boston 


JAMES RITCHEY 

Formerly Instructor in Wood-Working, Armour Institute of Technology 

V* 


C. C. ADAMS, B. S. 

Switchboard Engineer with General Electric Company 


BURTON L. GRAY 

Instructor in Foundry Practice, Worcester Polytechnic Institute 
Member Foundrymen’s Association 



Authors and Collaborators—Continued 


OSCAR E. PERRIGO, M. E. 

Consulting Mechanical Engineer 

Expert Patent Attorney 

American Society of Mechanical Engineers 

Author of “Modern Machine-Shop Construction, Equipment, and Management”, “Lathe 
Design, Construction, and Operation”, etc. 


MORRIS A. HALL, B. S. 

Formerly Managing Editor, Motor Life 

Editor, The Commercial Vehicle; Editor, The Automobile Journal, Motor Truck , etc. 

Author of “What Every Automobile Owner Should Know”, “Motorist’s First Aid Hand¬ 
book”, etc. 

Formerly Associate Editor, The Automobile 
Member, Society of Automobile Engineers 
Member, American Society of Mechanical Engineers 

ROBERT VALLETTE PERRY, B. S., M. E. 

Associate Professor of Machine Design, Armour Institute of Technology 


HAROLD W. ROBBINS, M. E. 

Formerly Instructor, Lewis Institute, and Armour Institute, Chicago 
Past Secretary, The Aero Club of Illinois 
Special Writer and Technical Investigator 

V* 


EDWARD B. WAITE 

Formerly Dean, and Head, Consulting Department, American School of Correspondence 
American Society of Mechanical Engineers 


WILLIAM C. STIMPSON 

Formerly Head Instructor in Foundry Work and Forging, Department of Science and 
Technology, Pratt Institute 


V 


JOHN JERNBERG 


Instructor in Forge Practice and Heat Treatment of Steel, Worcester Polytechnic 
Institute 

Member, Swedish Engineering Society 




JESSIE M. SHEPHERD, A. B. 

Head, Publication Department, American Technical Society 



Authorities Consulted 


F I "\KE editors have freely consulted the standard technical literature of 
America and Europe in the preparation of these volumes. They 
A desire to express their indebtedness, particularly, to the following 
eminent authorities, whose well-known treatises should be in the library of 
everyone interested in Modern Shop Practice. 

Grateful acknowledgment is here made also for the invaluable co-opera¬ 
tion of the foremost manufacturers and engineering firms, in making these 
volumes thoroughly representative of the best and latest practice in machine 
and pattern shops, foundries, and drafting rooms, and in the construction 
and operation of machine tools, and other classes of modern machinery; also 
for the valuable drawings and data, suggestions, criticisms, and other 
courtesies. 


C. L. GOODRICH 

Department Foreman, Pratt & Whitney Company 

Joint Author with F. A. Stanley of “Accurate Tool Work,” “Automatic Screw Machines 
and Tools” 

OSCAR E. PERRIGO, M. E. 

Consulting Mechanical Engineer 

Author of “Modern Machine-Shop Construction, Equipment, and Management”; “Lathe 
Design, Construction and Operation”; “Change Gear Devices” 

'V* 

JOHN LORD BACON 

Formerly Instructor in Forge Work, Lewis Institute, and Instructor in Shop Work, 
University of Chicago 

Author of “Forge Practice” 

V* 

JOSEPH V. WOODWORTH, M. E. 

Author of “American Tool Making,” “Punches, Dies, and Tools for Manufacturing in 
Presses,” “Dies, Their Construction and Use for the Modern Working of Sheet 
Metals,” “Gages and Gaging Systems,” “Grinding and Lapping,” “Drop Forging, 
Die Sinking and Machine Forming of Steel,” etc. 


FREDERICK A. HALSEY 

Editor Emeritus, American Machinist 
Author of “Methods of Machine Shop Work,” 
Draftsmen” 


‘Handbook for Machine Designers and 


WILLIAM KENT, A. M., M. E. 

Consulting Engineer; Formerly Dean of the L. C. Smith College of Applied Science, 
Syracuse University; Member of the American Society of Mechanical Engineers, etc. 
Author of “The Mechanical Engineer’s Pocket-Book,” “Strength of Materials,” “Steam 
Boiler Economy,” etc. 




Authorities Consulted—Continued 


FRED H. COLVIN 

Associate Editor of American Machinist 

Author of “Machine-Shop Calculations”; Joint Author with F. A. Stanley of “American 
Machinist’s Handbook,” “Machine Shop Primer,” “Hill Kink Books”; Joint Author 
with Lucius Haas of “Jigs and Fixtures,” etc. 


EDWARD R. MARKHAM 

Instructor in Shop Work, Harvard University and Rindge Technical School 
Consulting Expert in Heat Treatment of Steel 
Formerly Superintendent, Waltham Watch Tool Company 
American Society of Mechanical Engineers 


HARRY HUSE CAMPBELL 

Metallurgical Engineer, the Pennsylvania Steel Company 
Author of “The Manufacture and Properties of Iron and Steel” 


HUGO DIEMER, M. E. 

Professor of Industrial Engineering, Pennsylvania State College 

Author of "Factory Organization and Administration”; Joint Author with G. H. Resides 
of “Wood Turning” 


F. A. STANLEY 

Associate Editor of American Machinist 

Joint Author with F. H. Colvin of “American Machinist's Handbook,” “Machine Shop 
Primer,” and “Hill Kink Books”; Joint Author with C. L. Goodrich of “Accurate 
Tool Work,” “Automatic Screw Machines and Tools” 

V 

HENRY M. HOWE, B. S., A. M., LL. D. % 

Formerly Professor of Metallurgy, Columbia University 

Author of “Iron, Steel, and Other Alloys,” “Metallurgical Laboratory Notes” 


JOSHUA ROSE, M. E. 

Author of “Mechanical Drawing Self-Taught.” “Modern Steam Engineering,” “Steam 
• Boilers,” “The Slide Valve,” “Pattern Maker’s Assistant,” “Complete Machinist” 

V* 


P. S. DINGEY 

Associate Member, American Society of Mechanical Engineers 
Author of “Machinery Pattern Making” 



Authorities Consulted—Continued 


ROBERT GRIMSHAW, M. E. 


Author of “Steam Engine Catechism,” “Boiler Catechism,” “Locomotive Catechism,' 
"Engine Runner’s Catechism,” “Shop Kinks,” “Saw Filing,” etc. 


JOSEPH G. HORNER 

Associate Member of the Institution of Mechanical Engineers 

Author of “Pattern Making,” “Hoisting Machinery,” “Tools for Machinists and Wood¬ 
workers,” “Modern Milling Machines,” “Engineers’ Turning,” “Practical Metal 
Turning,” etc. 


THOMAS E. FRENCH, M. E. 

Professor of Engineering Drawing, Ohio State University 
Author of “Engineering Drawing” 

V 


WILLIAM JOHN MACQUORN RANKINE, LL. D., F. R. S. S. 


Civil Engineer; Late Regius Professor of Civil Engineering and Mechanics in the 
University of Glasgow, etc. 

Author of “Applied Mechanics,” “The Steam Engine,” “Civil Engineering,” “Useful 
Rules and Tables,” “Machinery and Mill Work,” “A Mechanical Textbook” 


^ / 


WALTER LEE CHENEY 


Joint Author with Fred H. Colvin of “Machine-Shop Arithmetic,” and “Engineer’s 
Arithmetic” 




GARDNER C. ANTHONY, A. M., Sc. D. 

Professor of Technical Drawing, and Dean of the Department of Engineering, Tufts 
College, Massachusetts 

Author of “Elements of Mechanical Drawing,” “Machine Drawing,” “The Essentials of 
Gearing” 

V* 

CHARLES W. REINHART 

Formerly Chief Draftsman, Engineering News 
Author of “Technic of Mechanical Drafting” 

V 

SIMPSON BOLLAND 

Author of “The Iron Founder,” “The Iron Founder’s Supplement.” “Encyclopedia of 
Founding,” “Dictionary of Foundry Terms,” etc. 

V* 

THOMAS D. WEST 

Practical Moulder and Foundry Manager; Member, American Society of Mechanical 
Engineers 

Author of “American Foundry Practice” 



Authorities Consulted—Continued 


WILLIAM RIPPER 


Professor of Mechanical Engineering in the Sheffield Technical School; Member of the 
.Institute of Mechanical Engineers 
Author of “Machine Drawing and Design,” “Steam,” etc. 


OSCAR J. BEALE 

Author of “Handbook for Apprenticed Machinists” 


*• 


JAMES LUKIN, B. A. 

Author of “Possibilities of Small Lathes,” “Simple Decorative Lathe Work,” “Turning 
for Beginners,” “The Lathe and Its Uses,” “The Forge and Lathe,” etc. 

V 

0. M. BECKER 

Author of “High Speed Steel—Its Manufacture, Use, and the Machines Required” 

F. W. BARROWS 

Author of “Practical Pattern Making” 




L. ELLIOTT BROOKES 

Author of the “Automobile Handbook,” “Practical Gas and Oil Engine Handbook,” 
“The Calculation of Horse-Power Made Easy,” “20th Century Machine-Shop 
Practice” 

V* 

STANLEY H. MOORE 

Member or Associate, American Society of Mechanical Engineers, American Institute of 
Electrical Engineers, Franklin Institute, etc. 

Author of “Mechanical Engineering and Machine-Shop Practice” 

CHARLES C. ALLEN 

Lecturer in Engineering, Municipal Technical Institute, Coventry, England 
Author of “Engineering Workshop Practice” 

BRADLEY STOUGHTON 

Consulting Engineer; Formerly Adjunct Professor, School of Mines, Columbia University 
Author of “The Metallurgy of Iron and Steel” 

V* 

F. W. TAYLOR, M. E. 

Late Member, American Society of Mechanical Engineers 
Author of “On the Art of Cutting Metals” 





. 




■i 


RADIAL DRILL BORING DEEP HOLE WITH TWIST DRILL 

Courtesy of American Tool Works, Cincinnati, Ohio 
































Foreword 


A LITTLE more than a century ago our mechanical devel- 
opment had its beginning when the first prime movers 
were invented and developed. With the development of ma¬ 
chines came the development of mechanics to run these 
machines, to fabricate the parts and assemble them into the 
finished articles. The evolution of both machines and mechan¬ 
ics has been marvelous, the accuracy of workmanship of today 
being easily two hundred times that of a century ago, and the 
speed of manufacture probably much more than this. Since 
that time one industry has helped to develop others until today 
the mines produce ore in large quantities to supply the iron, 
copper, and other metals; the great steel mills supply the raw 
or fabricated material; the foundries and forging shops fashion 
the many castings and forgings for the intricate machine to be 
built; the immense shops machine the parts and assemble them 
for the market. Everywhere we turn we find a manufactured 
article which has gone through these various changes from raw 
material to finished product. 

<L “Production'' methods have enormously increased the out¬ 
put of our shops and the machines which have made this de¬ 
velopment possible are of a diversified character—speed lathes, 
planers, multiple drillers, grinders, milling machines, stamping 
machines, die presses and the jigs, tools and dies which go 
with them—all of these have contributed to the accuracy and 
speed of manufacture. The demands of the automobile in¬ 
dustry have done wonders in hastening this development as 
the manufacture of the parts in duplicate was absolutely 
necessary in order to cheapen the price of the assembled ma¬ 
chines. The fact that many of the present-day automobiles 



are shipped “knocked down” to assembly points without ever 
having been put together is an eloquent testimonial to the 
accuracy with which the duplicate parts are built. Another 
contributing factor in modern production methods is the de¬ 
velopment of high speed steels which enable the operators to 
run the machines at speeds hitherto unattainable. 

®And yet with all this wonderful development of the machines 
themselves and the design of what are termed “automatics,” 
the workman has not lost his skill. In fact, one trip to a well- 
organized scientific machine shop will teach any skeptic 
that the intelligent workman who has contributed so largely 
to the mechanical developments of the past twenty years is 
more skilled, more intelligent, certainly better paid, and more 
interested in his work than ever. 

CBut this same skilled mechanic is today a specialist. He has no 
opportunity to build a complete machine or even a small part of 
one; his active work is carried on along rather narrow lines. 
Consequently, it is all the more necessary for him to have a 
standard reference work to help him in other shop lines with 
which he is unfamiliar. “Modern Shop Practice” is such a 
work—one which has been tested through six editions—and the 
practical treatises on the various shop subjects have been 
supplied by well-known teachers and practical men and are 
strictly up-to-date. The authors have at all times kept in mind 
the practical nature of their subjects and numerous shop kinks 
and other helpful suggestions have been introduced. It is the 
hope of the publishers that this new edition will supply the 
needs of both the skilled mechanic and the layman who is inter¬ 
ested in mechanical affairs. 

Cjn conclusion, grateful acknowledgment is given to the 
authors and collaborators — engineers and designers of wide 
practical experience and teachers of recognized ability—without 
whose co-operation this work would have been impossible. 


Table of Contents 


VOLUME I 

Machine Shop Work (Hand and Power Tools) By F. W. Turner 

and O. E. Perrigo; Revised by H. P. Fairfield t . . Page *11 

Measuring Tools: Angular Measurement (Gages, Rules, Squares, Bevels, Pro¬ 
tractors, Combination Sets), Linear Measurements (Carpenters’ Rule, Dividers, 
Micrometer Calipers, Vernier Calipers, Gages, Surface Plates) — Simple Hand 
Tools: Hammers, Cutting Tools, Files (Kinds, Correct Positions, Cleaning, Hand 
Scraping), Hand Punches, Drilling Tools (Drillers, Types of Drills, Care of Drills, 
Reamers), Hand Threading Tools (Taps, Threading Dies)—Power-Driven Tools: 

Lathes (Speed Lathes, Engine Lathes, Lathe Equipment, Lathe Operations 
(Mounting Work, Turning, Eccentric Turning, Boring Bars, Screw Cutting, 
Chasing), Drillers (Standard Types, Multiple Spindle. Radial Type), Planers. 
Shapers—Milling Machines: Milling Cutters, Types of Milling Machines (Bench 
Miller, Horizontal Type, Vertical Type, Duplex Milling Machines), Milling 
Operations—Grinding Machines—Laying Out Work—Suggestions 


Machine Shop Work (Gear Cutting, Turret Lathes and Screw 

Machines) . By O. E. Perrigo; Revised by H. P. Fairfield Page 205 

Gear Cutting: Theory, Spur Gears, Bevel Gears, Pitch Circle, Tooth Parts, Gear 
Design, Ratio of Gears, Tooth Curves, Internal Gears, Teeth of Racks, Involute 
Gears, Worm Gears, Spiral Gears, Helical Gears, Cutting Processes — Teeth 
Testing—Speed and Feed of Cutters—Lubrication—Commercial Types of Gear- 
Cutters—Turret Lathes: Classes of Turret Lathes, Cross-Slide, Monitor Lathe, 
Hand-Screw Machine, Wire-Feed Attachment—Tools: Centering Tools, Drills, 
Reamers, Boring Bars, Counterborers, etc.—Lathe Operation—Automatic Screw 
Machines: Drum Cams, Wire and Rod Feed, Commercial Types of Machines, 
Universal Screw Machine, Forms of Turrets, Forming Slide, Finishing Slide, 
Holders, Quick-Return Devices, Hollow Mills, Setting Up the Machine 

Machine Shop Work (Modern Manufacturing) 

. By H. P. Fairfield Page 277 

Machine Building vs. Machine Manufacturing — Production Methods: Single 
Purpose Machines, Special Cutting Speeds, Lubrication, Feeds, Automatic. 
Cold-Worked Metals, Die Casting Machine Parts—Molding Processes, Die Forg¬ 
ings, Heat Treatment, Ball Bearings, Drives, Jigs and Fixtures, Time Study— 
Production Machines: Grinding Machines (Usefulness, Cylinder Grinding, Wheel 
Traverse, Grinding Allowances, Abrasive Wheels, Grinding Methods), Milling 
Machines (Horizontal, Vertical, Planer Millers, Production Cutters), Drilling 
Machines (Heavy and Light High-Speed Drillers, Production Figures), Forming 
Machines (Turning Lathe, Lubrication, Automatic), Planing Machines, Broach¬ 
ing Machines—Cutting Tools: Materials, Tools—Jigs: Jig Design and Construc¬ 
tion (Drill Jigs, Tolerances, Guide Bushings, Operating Jig), Fixtures — Ball 
Bearings—Magnetic Chucks—Safety First 

Review Questions ..Page 361 

Index .Page 369 


* For page numbers, see foot of pages. 

fFor professional standing of authors, see list of Authors and Collaborators at 
front of volume. 





















MACHINE SHOP WORK 


PART I 


HAND=OPERATED TOOLS 

Simultaneous Use of Hand Tools and Machines. Machine 
shop work is usually understood to include all cold metal work in 
which a portion of the metal is removed to make the piece of the 
required shape and size either by power-driven or hand tools. How¬ 
ever, there are some branches of cold metal work, such as sheet- 
iron work and coppersmithing, that are not included in machine 
shop work. 

As the hand-operated tools are much simpler, and as the opera¬ 
tions performed with them are in every case more typical, their 
description and use should precede that of power-driven tools. It 
should be clearly understood, however, that machine shop practice 
involves the use of both classes at the same time. Even hand 
tools are not used in the same order on different classes of work; 
it is, therefore, impossible to describe them in the order of use. 
Simplicity of construction and operation will be the guide for treat¬ 
ment in the following pages. 

MEASURING TOOLS 
ANGULAR MEASUREMENT 

Surface Gage. The surface gage is used in laying out work 
for the bench, lathe, or planer. The ordinary form consists of a 
heavy base, an upright which is firmly attached to the base, and a 
scriber or scratch awl. In the universal gage, the upright is pivoted 
at the base so that it may be used at any angle. In some forms 
the base is grooved in order that the gage may be used on cylindrical 
work as well as on flat surfaces, Fig. 1. 

To use the gage, the part of the work to be laid out must be 
prepared so that lines drawn on the surface will show distinctly. 
A rough or unfinished surface is covered with chalk, a finished or 
bright surface should be copper-plated by applying a thin coating 


11 



2 


MACHINE SHOP WORK 


of copper sulphate solution with a brush or a piece of waste. In 
use, the work and the gage are then placed on a true surface and the 
scriber adjusted to the desired height. The lines are drawn by 
moving the surface gage along on the true surface, keeping the point 
in contact with the work. After scribing the lines, it is well to 
place light prickpunch marks at frequent intervals along the lines, 



Fig. 1. Universal Surface Gage 
Courtesy of the L. S. Starrett Company , Athol , Massachusetts 


so that the position may be located if the chalk or copper sulphate 
becomes effaced. 

Straightedge. The straightedge consists, in its simplest form, 
of a thin flat piece of steel, often unhardened, with accurately 
finished straightedges. The very small sizes used in fine work are 
occasionally made with a hardened knife edge. A non-conducting 
handle is sometimes used with the small sizes to prevent distortion 
from the unequal heating due to handling. The short lengths 
used for ordinary shop purposes have one edge beveled and are 


12 


MACHINE SHOP WORK 


3 


thick enough to avoid bending, Fig. 2. The larger sizes, from 3 
to 10 feet or more in length, are usually made of cast iron with 
one finished edge. The metal 
is so distributed as to combine 
lightness with great rigidity, the 
tendency of the ends to drop 
being resisted by the truss-like 
form of the casting shown in 
Fig. 3. The flat form is used, 
in connection with the scriber, 
to draw accurate straight lines 
on plane surfaces. All styles are 
used to test the truth of plane surfaces by placing the straightedge on 
the surface to be tested in not less than the six positions shown in Fig. 4. 



Fig. 2. Steel Straightedge 




Fig. 3. Cast-Iron Straightedge 


Keyseat Rule. For drawing lines and laying off distances 
on curved surfaces, such as shafts, a combination of two straight- 



Fig. 4. Diagram Illustrating Use of Straightedge 


edges, or a straightedge and a rule, is used. This is often called 
a keyseat rule because its chief use is laying out keysways on shafts. 


13 



































4 


MACHINE SHOP WORK 


However, many machinists call it a box rule. It is usually made 
in one piece, although some manufacturers provide clamps by which 
the two separate pieces are held at right angles to one another. 



Fig. 5. Keyseat Rule 

Courtesy of L. S. Starrett Company, Athol, Massachusetts 


A more simple combination is shown in Fig. 5, the second scale 
being represented by two special clamps. 

Flat Square. The simplest form of square, called the flat square, 
Fig. 6, is a combination of two straightedges at right angles. This 
is a useful form where the square is laid on the work. One blade 
is usually graduated on the inner edge, and the other on the 
outer edge. 

Try Square. The try square, Fig. 7, consists of a beam and 
a blade at right angles. The beam is much thicker than the blade 



and somewhat shorter. Try squares are made both unhardened 
and hardened. The unhardened form has graduations on one 
edge and is termed a graduated try square. The hardened type 


14 









MACHINE SHOP WORK 


always has a hardened blade, sometimes a hardened beam as well, 
and is not graduated. 

1 he try square is used as a guide to draw lines at right angles 
to each other and to given surfaces; to erect and test perpendic¬ 
ulars to plane -- — —< 

surfaces; to test % thel.s.starrettco. * 

the truth of a N<?20 

. -- _ ATHOL. MASS.U.S.A. 

given surface at ? _ 

right angles to 

another surface; in short, it is used wherever an accu¬ 
rate measurement of 90 degrees is required. When 
used for testing the relation of two surfaces, the beam 
is pressed closely against the correct surface, and the 
blade is brought carefully down to the surface under 
consideration. This does not prove more than that 
a line at the particular point tested is or is not at 
right angles to the true surface. By using the blade 
as a straightedge parallel to the true surface, errors 
in that direction may be corrected and the surface be made plane. 

Bevel. In many cases it is necessary to test the relation of 
lines and surfaces which are not at right angles to each other. For 




Fig. 8. Universal Bevel 

Courtesy of L. S. Starrett Company, Athol, Massachusetts 


this purpose a bevel is used in which what corresponds to the blade 
of the square is made adjustable. Its construction is seen in 
Fig. 8; its use is similar to that of the square. 


15 





















6 


MACHINE SHOP WORK 


Protractor. The bevel can be adjusted only by direct appli¬ 
cation to lines or surfaces having the proper angular relation. It 
often happens that such adjustment is not feasible and, therefore, 
a registering device, in the form of a graduated arc, is applied to 
the bevel, making what is known as a protractor, Fig. 9. This 
tool can be used to find the angular relation in degrees or to produce 
that relation by setting to the proper point on the graduated arc. 

Center Square. As the center of a circle is found at the inter¬ 
section of any two diameters, an instrujnent for readily finding 
that point is a great convenience. In Fig. 10 is shown a combina¬ 
tion straightedge and square, called a center square, w T hich accom¬ 
plishes this result. As one edge of the rule bisects the angle of the 
square, it is evident that a line drawn by that edge passes through 



Fig. 9. Protractor 

Courtesy of L. S. Starrett Company, Athol, Massachusetts 


the center of any circular piece to which the square is applied. 
Centering the ends of round bars or circular work of any kind is 
the principal use of this tool. 

Combination Set. The center square, bevel, and protractor 
are furnished in a combination set as shown in Fig. 11. The ability 
to change the length of the blade is one of the great benefits of this 
construction. 

LINEAR MEASUREMENT 

The testing tools thus far described are used for comparing the 
angular relation of lines and surfaces and may be called tools for 
angular measurement. We now turn to the consideration of instru¬ 
ments for measuring distances and sizes, or tools for linear meas¬ 
urement. 


16 















MACHINE SHOP WORK 


7 


Carpenter’s Rule. The most common tool for linear meas¬ 
urements, and one which hardly requires description, is the so-called 
carpenter’s, or two-foot, rule. This is v6ry convenient for the 



machinist in making measurements which are not required to be 
very accurate. 

Steel Rule. For work of greater refinement, the standard 
steel rule, Fig. 12, is used. This is in reality a graduated straight- 



Fig. 11. Combination Set 

Courtesy of L. S. Starrelt Company, Athol, Massachusetts 


edge and, as such, forms a part of several tools already described. 
The most common form of steel rule is flat, varying from 1 to 48 
inches in length, and carefully hardened and ground. The grad- 


17 











8 


MACHINE SHOP WORK 


uations in the better class of rules are cut with a dividing engine, 
although the lines may be etched on the surface with a fair degree 
of accuracy. A thin and somewhat narrower form, called a flexible 
rule, is made in sizes from 4 to 36 inches. What are known as nar¬ 
row rules are obtainable from 4 to 36 inches and are of great con¬ 
venience in certain cases. Besides these shapes, square rules are 
made in sizes from 3 to 6 inches in length, and the triangular form 
varies in length from 3 to 12 inches. Steel rules with the English 
system of graduation can be obtained with the inches divided in 
eighths, sixteenths, thirty-seconds, sixty-fourths; twelfths, twenty- 
fourths; tenths, twentieths, fiftieths, and hundredths. Special 
rules are made with graduations especially adapted to such uses as 
gear blank sizing, etc. 

The ends of flat rules are sometimes graduated, making what 
might be called a very short rule with a handle. Flat rules are 


i- 

U|l l|l|l|l 

i 


'iii|iii|iii|ni 

WV'm 

<m -n 
co — 

ir 

■ i Hi , 

■ 11 111 

r 1 ' i 1 i 

1111 ill 


Fig. 12. Steel Rule 


sometimes graduated with metric divisions as fine as one milli¬ 
meter, and from 5 centimeters to 1 meter in length. 

Dividers. For transferring and comparing distances, dividers 
are commonly used. They are classified according to the style of 
joint and the length of the leg. The most simple joint is the 
friction and, like all frictional devices, is hard to set accurately. Lock- 
joint dividers can be moved freely to approximately the right 
position, the joint locked, and the adjusting screw used for the 
final setting. 

Wing dividers, Fig. 13, are of about the same construction 
as the lock joint, except that the fastening is made on the wing 
instead of at the pivot. The best of all forms has a spring adjust¬ 
ment as shown in Fig. 14. In this type, a spring tends to open the 
dividers, and the legs are closed against the spring by a nut working 
on a screw which is fastened to one leg and passes freely through 
the other. The length of dividers varies from 2\ to 10 inches. 


18 



















MACHINE SHOP WORK 


9 


The distance to which dividers can be opened is generally about 
equal to the length of the leg. For distances above 10 inches, tram¬ 
mel points, Fig. 15, are convenient. They consist of hardened 
steel points attached to metal sockets and can be used on rods of 
any length. One point may have a spring adjustment and, in 
that case, can be set in the same manner as a pair of wing dividers. 




Fig. 14. Tool-Makers’ Dividers 
Courtesy of Brown and Sharpe Manu¬ 
facturing Company, Provi¬ 
dence, Rhode Island 


Calipers. Outside and Inside Calipers. Instead of having 
straight legs with sharp points, caliper legs are bent and have blunt 
points. As distances are to be measured both outside and inside 
of solid bodies, we have outside and inside calipers. The legs of 
outside calipers have a large curvature so that the calipers may be 
passed over cylinders of their greatest capacity. 

Inside calipers, Fig. 16, are more like dividers in general appear¬ 
ance, the ends being bent outward slightly and the points rounded. 
The same styles of joints used in dividers are used in calipers, and 


19 





10 


MACHINE SHOP WORK 



Er, ± 


Fig. 15. Steel Beam Trammels 

Courtesy of Brown and Sharpe Manufacturing Company, Providence, Rhode Island 



Fig. 16. Brown and Sharpe Inside 
Transfer Calipers 


Fig. 17. Brown and Sharpe Outside 
Transfer Calipers 


20 






























MACHINE SHOP WORK 


11 


the size of calipers is also designated by the distance from the joint 
to the end of the leg. Spring calipers are made in sizes from 2\ 
to 8 inches, while the other styles vary up to 24 inches. 

Transfer Calipers. As it is sometimes necessary to make 
measurements behind shoulders and in chambered cavities where 
the ordinary calipers could not be removed after setting, it is neces¬ 
sary to have calipers so arranged that they may be set, changed to 
clear the obstruction, and then reset accurately in the first position. 
This is accomplished by transfer calipers, Fig. 17, in which one 
leg is temporarily fastened to a stub or false leg. After setting, 
this leg may be moved away from the stub, the calipers withdrawn, 
and the leg again placed in contact with the stub; the points will 
then be found to occupy the 
same position as w T hen first 
set. Small curved legs may 
be used in place of points or 
trammels in calipering large 
objects. 

Both dividers and cali¬ 
pers are usually set by means 
of a scale. In setting divi¬ 
ders, place one point in a 
graduation of the scale and 
move the other until it falls 
easily into another graduation which gives the required distance. 
Outside calipers are often set by placing one leg against the end 
of the scale and moving the other until it is opposite the middle 
of the graduation giving the required length. As the graduations 
are not mathematical lines but have an appreciable width, this 
last precaution is one of great importance. Inside calipers are 
set by placing both the scale and the caliper toe against a plane 
surface, as shown in Fig. 18; the other toe is then set the same as 
the outside caliper. 

Caliper legs are comparatively slender, spring easily, and care 
must be taken in using them to see that the contact with the object 
being tested is very light. It is an easy matter to spring calipers 
of common sizes as much as one-sixteenth of an inch unless a 
gentle touch is used in handling them. 



21 









12 


MACHINE SHOP WORK 


Caliper Square. The caliper square is made by attaching a 
movable blade to the common square. In the ordinary forms it 
closely resembles a steel rule with two arms extending from it at 
right angles, one fixed near the end and the adjustable arm sliding 
along the scale with a clamping device for adjusting this movable 
arm. In order that the movable arm may be set accurately, caliper 
squares, Fig. 19, as at present constructed have two clamps for the 
movable arm. The one carrying the thumb nut is to be first clamped 
in approximately the right position, the clamp on the movable 
arm being secured after the adjustment has been made by the nut. 



Fig 19. Caliper Square 

Courtesy of Brown nrul Sharpe Manufacturing Company, Providence, Rhode Island 


The sizes used vary from 3 inches up, and are limited only by the 
length of rule obtainable. 

Micrometers. For measurements which are required to be 
more accurate than can be obtained by the preceding forms of 
calipering devices, the micrometer caliper, Fig. 20, is used. The 
accuracy of its measurements is determined, not by direct setting 
to two lines, but by finely dividing the pitch of the measuring screw 
and furnishing means for reading these subdivisions. It is a regis¬ 
tering as well as an indicating caliper, and thus serves the purpose 
of a common caliper in combination with a rule, but with a much 
greater degree of accuracy. 

The micrometer caliper consists, essentially, of a crescent¬ 
shaped frame carrying a hardened steel anvil B at one end and a 


22 


















MACHINE SHOP WORK 


13 


nut of fine pitch at the other, the axis of the nut being at right angles 
to the face of the anvil. The outside of the nut A forms a pro¬ 
jection beyond the crescent that is called the barrel. The measuring 
screw consists of a fine-pitched screw to fit the nut, combined with 
a measuring point C, having a face parallel with that of the anvil. 
Firmly attached to the outer end of this screw is a thimble D, fitting 
closely over the barrel; the edge of this thimble is beveled so that 
graduations placed on the edge come very close to the barrel. A 
reference line is drawn on the barrel parallel to its axis and graduated 
to represent the pitch of the screw. The chamfered edge of the 
thimble is so divided that the movement of one division past the 
reference line on the barrel indicates a movement of the measuring 



Fig. 20. Transparent View of Micrometer Caliper with Friction Stop 
Courtesy of L. S. Starrett Company, Athol, Massachusetts 


point of one-thousandth of an inch. For example: if the pitch 
of the measuring screw is one-hundredth of an inch, there should 
be 10 divisions on the thimble, if one-fiftieth of an inch, 20 divisions; 
if one-fortieth of an inch, 25 divisions; if one twenty-fifth of an 
inch, 40 divisions. Measuring screws having a pitch of one-fortieth 
of an inch are usually used, and every fourth division on the 
barrel lengthened and numbered to indicate tenths of an inch, as 
shown in Fig. 21. 

In using the micrometer caliper, it should not be set at the 
size required and pushed over the work, but should first be opened, 
then screwed down until the measuring point C and anvil B are 
in contact with the work; the size may then be read from the relation 
of the thimble to the reference line on the barrel. The proper degree 


23 






14 


MACHINE SHOP WORK 


of pressure to be applied to the screw is acquired only after extended 
practice, and some manufacturers place a friction device on the 
thimble so that undue pressure cannot be exerted. 

The micrometer caliper will not only indicate that the work 
is too large or too small, but will also show exactly the amount 
by which it differs from the desired measurement. This is a great 
improvement over the rigid form of calipers, and enables the work¬ 
man to judge more accurately the progress of the work. As the 
micrometer caliper is rapidly coming into favor in spite of its cost, 
it has been described more at length than the common forms pre¬ 
viously considered. 

The range of motion of the measuring screw is usually limited 
to one inch, but various devices give the micrometer caliper a 



Fig. 21. Ordinary Micrometer Caliper Showing Typical Reading 


larger range of action. Micrometer calipers may now be purchased 
in combinations or sets, with a range from zero to 20 inches. 

The application of the micrometer principle to inside meas¬ 
urements is not in general use, but is easy to arrange, and makes 
a very simple instrument, as shown in‘Fig. 22. It consists of an 
ordinary micrometer head, except that the outer end of the thim¬ 
ble carries a contact point, attached to a measuring rod which 
may be of any length. - The shortest distance that can be measured 
with this device is about 2 inches, but there is hardly any limit in 
length, as the rigidity of the rod is easily provided for. It is evi¬ 
dent that such rigidity is harder to obtain in the curved shape 
necessary for outside measurement and thus limits this form to 
about 20 inches, as above stated. The contact points in the 
outside type are parallel plane surfaces, and in the inside form they 


24 














MACHINE SHOP WORK 


15 


are rounded points of small radius. Outside micrometers are pro¬ 
vided with contact points of varying forms for measuring paper, 
threads, walls of tubes, etc. 

Reading the Micrometer . Reading in thousandths. As stated, 
the micrometer screw has usually forty threads per inch and the 
thimble has twenty-five divisions on its circumference. The barrel 
is divided to correspond to the pitch of the screw with each fourth 
division numbered. In reading the indicated measurement, first 
note the highest number visible on the barrel and call it hundreds 



Fig. 22. Inside Micrometers 
Courtesy of L. S. Starrett Company, Athol, Massachusetts 


of thousands—in Fig. 21 it is 400 thousandths or .400; then 
read the short divisions on the barrel, calling the first division 25 
thousandths, or .025; the second, 50 thousandths, or .050; and the 
third, 75 thousandths, or .075. In Fig. 21 the third division is the 
last one visible. Now read the number indicated on the thimble, 
that is, the number that has passed the line running lengthwise. In 
the figure it is 16; or 16| if the reading is to be finer than thousandths. 
Add this reading to the readings of the short divisions, thus: 75+ 
16| = 91J; this is .091|. Adding the .400 to this we get .491J. This 
means that the distance from the anvil to the measuring point is 


25 
































16 


MACHINE SHOP WORK 


tVoVV of an inch, or .4915 inch. If the micrometer caliper is a 
good one, we may be sure the distance is between .491 inch and 
.492 inch. 

Reading to Ten-Thousandths. In reading measurements finer 
than thousandths, use is made of a Vernier. The following descrip¬ 
tion tells how to read a ten-thousandths micrometer: As applied to 
a micrometer, the Vernier consists of ten divisions on the sleeve 
which occupy the same space as nine divisions on the thimble. The 
difference of width of one of the ten spaces on the sleeve and one of 
the nine spaces on the thimble is one-tenth of a space on the thimble. 
In Fig. 23 at B, the third line from the zero on the thimble coincides 
with the first line on the sleeve. In opening the tool by turning the 



Fig. 23. Diagrams Showing How to Read Micrometer Caliper 


thimble to the left, each space on the thimble represents an opening 
of the tool equal to one-thousandth of an inch. If the thimble be 
turned so the lines marked 5 and 2 coincide, the tool will have been 
opened two-tenths of one-thousandth, or 2 ten-thousandths. At C 
the thimble has been turned until line 10 matches with line 7 on the 
sleeve. The tool has therefore been opened 7 ten-thousandths. 
Therefore, first note the thousandths as in reading the ordinary 
micrometer, then observe the line on the sleeve which matches with a 
line Qn the thimble. If it is the second line, marked 1, add one 
ten-thousandth to the previous reading; if the third line, marked 2 , 
add 2 ten-thousandths, etc. 

Vernier Calipers. A common use of a Vernier is its application 
to a caliper square, termed a Vernier caliper. Fig. 24 shows a repre¬ 
sentative tool. 


26 



























MACHINE SHOP WORK 


17 


How to Read the Vernier, The following text represents the 
L. S. Starrett instructions for reading their tool: 

The scale of the tool is graduated in fortieths, or .025 of an inch, every 
fourth division, representing a tenth of an inch, being numbered. On the Ver¬ 
nier plate is a space divided into twenty-five parts and numbered 0, 5, 10, 15, 
20, 25. The twenty-five divisions on the Vernier occupy the same space as the 
twenty-four divisions on the scale. 

The difference between the width of one of the twenty-five spaces on the 
Vernier and one of the twenty-four spaces on the scale is, therefore, 2 s of or 




Fig. 24. Front and Back View of Vernier Caliper 
Courtesy of L. S. Starrett Company, Athol, Massachusetts 


Tooo of an inch. If the Vernier is set so that the 0 line on the Vernier coincides 
with the 0 line on the scale, the next two lines will not coincide by tooo °f an 
inch; the next lines will be two thousandths apart, and *_o on. 

To read the tool, note how many inches—tenths, or .100, and fortieths, or 
.025—the 0 mark on the Vernier is from the 0 mark on the scale; then note the 
number of divisions on the Vernier from 0 to a line which exactly coincides with 
a line on the scale. 

In Fig. 25 the Vernier has been moved to the right one and four-tenths and 
one-fortieth inches (1.425"), as shown on the scale, and the eleventh line on the 
Vernier coincides with a line on the scale. Eleven thousandths of an inch are 
therefore to be added to the reading on the scale, and the total reading is one and 
four hundred and thirty-six thousandths inches (1.436"), which is the distance 
the jaws of the tool have been opened. 


27 





























18 


MACHINE SHOP WORK 


In making inside measurements, the width of the jaws, as given in the list, 
is to be added to the apparent readings on the side having the Vernier to allow 



Fig. 25. Enlarged View of Vernier 


2. What are the readings of 
and 27? 


for the space occupied by the meas¬ 
uring points. No such allowance is 
necessary when using the back side, 
without Vernier, as the two lines 
marked “in” and “out” indicate inside 
and outside measurements. 

EXAMPLES FOR PRACTICE 

1. A micrometer caliper shows a 
reading of .463; how many times must 
the thimble be turned to produce a 
reading of .587? (Assume 40 threads 
per inch.) Ans. 41^ times 

micrometer calipers shown in Figs. 26 

Ans. .039 


3. State the readings of the micrometer calipers shown in Figs. 28 and 29. 

Ans. .1546 




1: 

| r? 

_S 

U- 


— 

r 7 





Figs. 26 and 27. Positions of Caliper for 
Example 2 


Figs. 28 and 29. Positions of Caliper for 
Example 3 


4. Give the readings of the micrometer calipers shown in Figs. 30 

and 31. Ans. .7398 

5. Sketch the front and back of a micrometer caliper when the reading 
is .6327. 

6. What is the reading of the Vernier and scale when in position Fig. 32? 

Ans. 6.36 

Fixed Gages. While the adjustable tools just described are 
available for a large range of work, gages of one dimension, or fixed 
gages, are used to a considerable extent, especially in shops where 
work of a duplicate character is produced in large quantities. These 
may be used for standards to which adjustable gages may be set, 


28 

































































MACHINE SHOP WORK 


19 


or used directly in connection with the work in the same manner as 
an adjustable gage. One form of such gages for comparisons of 
length is a steel rod with the ends 
carefully ground so that the distance 
required may be quickly and accu¬ 
rately determined. In one form the 
ends are parallel plane surfaces, 
and in another the ends are sec¬ 
tions of a sphere of the same diam¬ 
eter as the length of the rod. Both 
these forms are illustrated in Fig. 33. 

Another form of gage for the same 
purpose consists of hardened and 
ground steel discs, Fig. 34, to which 
calipers and similar tools may be 
set, and which may be used also to 



Figs. 30 and 31. Positions of Caliper 
for Example 4 

For the latter purpose, 


test the size of holes by direct application, 
handles are provided by which the discs can be conveniently 
manipulated. 



G 

0 12 3 4! 
1 1 1 1 1 

5 6 7 8 9 10 

MINI 


f 

11 

1 2 

i 

IIMM 

3 4 3 6 

1 

k < 

n 

111 

' 2 3 < 

r 

M II M 

i 5 6 7 8 9 

1 ' 


Plug and Ring Gages. 

Plug and ring gages, Fig. 

35, furnish accurate and 
convenient standards for 
the production of dupli¬ 
cate parts of machines. The same result is attained by the caliper 
gage, Fig. 36, which combines the two gages in one piece. In 


Fig. 32. Position of Vernier for Example 6 





this form the external gage has parallel plane surfaces and the 
internal gage is a section of a cylinder. In sizes above 3 inches, 


29 





































20 


MACHINE SHOP WORK 


the caliper gage is usually made in two parts, making the tool easier 
to handle. 

As is indicated by the cost of these gages, the exact duplication 
of such exact sizes in quantities would mean a cost that would be 

prohibitive in machine con¬ 
struction. The limit of error 
in the standard gages just 
described is never over one 
ten-thousandth of an inch at a 
standard temperature, which is 
usually taken as 70° F. Ordi¬ 
nary machine parts do not 
require such accuracy, and it is 
usual to allow a limit of error 
which is in accordance with the 
class of work being produced. 

Limit Gages. For testing sizes and dimensions, both at the 
machine and in the inspection department, combination fixed gages, 



Fig. 34. Set of Ground Steel Disc Gages 
Courtesy of Brown and Sharpe Manufacturing 
Company, Providence, Rhode Island 



Fig. 35. Typical Plug and Ring Gages 

Courtesy of Brown and Sharpe Manufacturing Company, Providence, Rhode Island 



Fig. 36. Caliper Gages 

Courtesy of Brown and Sharpe Manufacturing Company, Providence, Rhode Island 

known as limit gages, are employed. These are made both for 
external and internal measurements. The external gage, Fig. 37, is 


30 


























MACHINE SHOP WORK 


21 


for testing pieces supposed to be .250 inch in diameter. As indicated 
by the figures on the gage, the piece is allowed a variation of .0005 
inch over and .001 inch under the nominal size. The words “go on” 
and “not go on”, stamped near the ends, indicate clearly how the 



Fig. 37. Limit Gage with Jaws Opposite 




Ts 

8 - 


Fig. 39. Limit Gage for Holes 


gage is used. A more convenient arrangement of this gage is shown 
in Fig. 38, in which the work must enter the first parallel opening, 
but must not pass through the second. In this form, one motion 
tests the piece for variation above and below the standard. Fig. 39 
shows a limit gage for holes, 
the end marked “go in” 
being required to pass into 
the hole, while the other 
end, marked “not go in”, 
must not enter. An arrange¬ 
ment of the internal limit gage similar to the external gage of Fig. 38 
is shown in Fig. 40, and has the same advantages. 

In some classes of work no variation is allowed over the stand¬ 
ard size, and in other classes no variation is allowed under the nom¬ 
inal size. The amount of 
variation allowed in any 
case is governed by the class 
of work and the intended 
use of the piece. As these 
allowances are not uniform, 
such gages are not kept in stock but are made only to order. 

For many years gages of an entirely different character have 
been used in the measurement of wire, small rods, and sheet metal. 
The sizes have been designated, not by the diameter or any definite 
unit, but by a number or letter in a purely arbitrary manner. Even 
in the same gage, the sizes do not advance in any regular order. 


= 


P 1.249- l.25l=z: 


gggg 

'1 | • SP 


Fig. 40. Limit Gage for Holes with Limits 
in Series 


31 






















22 


MACHINE SHOP WORK 




Fig. 41. Cast-Iron Surface Plate 
Courtesy of Brown and Sharpe Manufacturing Company, 
Providence, Rhode Island 


The matter is still further complicated by the fact that in one gage 
large numbers indicate large sizes, while in another, the smaller 
numbers mark the large diameters. Another source of annoyance 

lies in the fact that such 
gages are cheaply made 
and cannot be relied 
upon to be duplicates of 
one another. Most of 
these gages had their 
origin in days when 
r e f 4 i n e d measurements 
were not common, but 
since the use of the 
micrometer caliper has 
become almost universal, there seems to be no good reason why all 
sizes should not be expressed in thousandths of an inch, thus avoiding 

the troubles incident to 
the use of the arbitrary 
gages. 

Surface Plates. For 

the production of accurate 
plane surfaces the use of 
the straightedge is not 
sufficient. Such surfaces 
should be compared with 
standard surfaces, called 
surface plates, Fig. 41. A 
surface plate is a cast- 
iron plate strongly ribbed 
on the back to prevent 
distortion, and supported 
on three points to insure a 
uniform base. Their pro¬ 
duction and use will be 
described under the head of “Scraping”. They may be had in 
sizes varying from 3 inches by 4 inches to 36 inches by 72 inches. 

Work Bench. The machinist’s bench at which hand work is 
ordinarily performed should be of substantial character, about 2 


Fig. 42. Work Bench 

Courtesy of Brown and Sharpe Manufacturing Com¬ 
pany, Providence, Rhode Island 


32 


































MACHINE SHOP WORK 


23 


feet 10 inches from the floor and 2 feet 3 inches wide, Fig. 42. For 
the sake of economy it is usual to have a 2 \- or 3-inch plank at the 
front to which the vises are fastened and on which all the heavy work 
is done, w hile the rear of the bench is made from 1-inch lumber. Maple 
and birch are preferred as materials for a bench, although ash makes 
a very good substitute. 

Work Vises. In order that w T ork may be held rigidly for the 
performance of hand operations, the machinist uses wFat is termed 
a vise. They are made in a great variety of forms and sizes, but all 



consists essentially of a fixed jaw, a movable jaw^, a screw, a nut fas¬ 
tened to the fixed jaw, and a handle by which the screw is turned 
in the nut and the movable jaw brought into position. The sec¬ 
tional view, Fig. 43, shows these parts clearly and also a device, 
present in some form in all vises, by which the movable jaw is sep¬ 
arated from the fixed jaw when the screw is backed out in the nut. 

In the machinist’s vise, both jaws are made of cast iron with 
removable faces of cast steel. These may be checkered to provide 
a firm grip for heavy work, or may be smooth to avoid marking the 
surface of the plate operated upon. When holding soft metal, even 


33 



































24 


MACHINE SHOP WORK 


the smooth steel jaws would mar the surface; and in such cases it is 
customary to use false jaws of brass or Babbitt metal, or to fasten 
leather or paper directly to the steel jaws. The screw and handle 
are made from steel and the nut from malleable iron. 

The common method of fastening a vise to the bench is by 
means of the fixed base shown in Fig. 43, although a swivel base 
such as is shown in Fig. 44 is preferable. The vise shown in Fig. 44 
also has a swivel jaw, which enables it to hold tapered work securely. 
This swivel jaw is provided with a locking-pin, which fixes the jaws 



Fig. 44. Swivel Work Vise 


in a parallel position. The height of the vise from the floor depends 
somewhat on the class of work to be performed, but a general rule 
is to have the top of the jaws about 1J inches below the point of the 
elbow when standing erect beside the vise. 

HAMMERS 

Classification. The machinist uses hammers of three shapes: 
ball peen, cross peen, and straight peen, Fig. 45. The ball peen is 
the most common; it varies in weight from 4 ounces to 3 pounds. 
The cross peen and straight peen hammers vary from 4 ounces to 2 
pounds and are used principally in riveting. Hammers are made 


34 








































MACHINE SHOP WORK 


25 


from a good grade of tool steel, hardened, and drawn to a blue 
color at the eye and a dark straw on the face and peen. The eye is 
elliptical in shape, and the handle is fastened by driving wedges, 
either wood or iron, into the end of the handle, thus spreading it to 
fill the eye. The handle is of hard wood, preferably hickory, and of 
a length suited to the weight of the hammerhead. When the handle 
is properly inserted, the axis of the head stands at right angles to 
the axis of the handle. 

Soft Hammers. Soft hammers are used for striking heavy 
blows where the steel hammer would bruise the metal or mar the 
surface. They are made of rawhide, copper, or Babbitt metal, and 
vary in weight from 6 ounces to 0 pounds. They are subject to 



Fig. 45. Hand Hammers 


rapid wear, but are indispensable in setting up and taking down 
machinery. Those of metal are so constructed that the soft metal 
can be recast in the handle. 

CUTTING TOOLS 

Chisels. The simplest form of metal-cutting tool is the chisel. 
The several types in common use are shown in Fig. 46. 

Flat Chisel . The flat chisel is used for snagging castings, for 
chipping surfaces having less width than the edge of the chisel, and 
for all general chipping operations. It is the form most commonly 
used, and is often called the cold chisel. Generally it has a cutting 
edge about an eighth of an inch wider than the stock from which it 
is forged. 

Cape Chisel. The cape chisel is used for cutting keyways, 
channels, etc., and also for breaking up surfaces too wide to chip 
with the flat chisel alone. Channels are driven across such a sur¬ 
face, leaving raised portions or “lands” to be removed by the flat 


35 











26 


MACHINE SHOP WORK 


chisel. The cutting edge of this chisel is usually an eighth of an 
inch narrower than the shank, and the part just in the rear of the 
cutting edge is made thin enough to avoid binding in the slot. As 
this weakens the chisel, it is made comparatively thick in the plane 
at right angles to the cutting edge. 

Diamond Point The diamond point chisel is made by drawing 
out the end of the stock to about ■£$ inch square, and grinding the 
end at an angle with the axis of the chisel, leaving a diamond-shaped 
point. It is used for drawing holes, making oil grooves, and cutting 
holes in flat plates. 

Round Nose. The small round-nosed chisel is cylindrical in 
section near the cutting end, the edge being ground at an angle of 
60 degrees with the axis of the chisel. When used to “draw” the 
starting of drilled holes to bring them concentric with the drilling 



Fig. 46. Hand Chisels 


circles, they are called center chisels. The round-nosed chisel is 
also used for cutting channels, such as oil grooves and similar work. 
The larger sizes of round-nosed chisels are of the general shape of 
the cape chisel with one edge rounded, making a convex cutting 
edge. Large round bottomed channels and all concave surfaces are 
the proper work of the round-nosed chisel. 

All the accompanying forms should be made from a good grade 
of tool steel, carefully forged, hardened, and tempered to a purple 
color. The stock generally used is octagonal, and the chisels for 
heavy work are about 8 inches long and f inch in diameter. 

Cutting Edge of Chisel. The two bevels forming the cutting 
edge of a chisel should make with each other as small an angle as is 
possible without leaving the cutting edge weak. If the angle is too 
small, the chisel will soon become dull, while if large, more force will 


36 
















MACHINE SHOP WORK 


27 


be required to drive it. The best angle for cutting cast iron, all 
things considered, is about 70 degrees, while for wrought iron and 
mild steel a slightly smaller angle, say 60 degrees, will be better. 
When there are two bevels, they should be alike in width and form 
equal angles w ith the center line of the chisel. Small round-nosed 
chisels and some slotting chisels are ground one-sided, that is, wdth 
but one bevel like a wood chisel. The angle between the surfaces 
w r hich form the cutting 
edge should be the same, 
whether these surfaces 
are both bevels, or one 
a bevel and the other 
the straight side of the 
chisel. In a one-sided 
chisel, therefore, the 
angle that the bevel 
forms w T ith the center line 
of the chisel should be 
twice as large as in one 
having tw T o bevels. 

To cut well, chisels 
should be sharp and, 
therefore, should be 
ground at once when 
they become dull. This 
may be done on an 
emery or carborundum 
wheel, not finer than 
No. 60, care being taken 
to avoid heating, w T hich draw r s the temper and spoils the tool. 

Chipping. Chipping is a term applied to the removal of metal 
with the cold chisel and hammer. The degree of accuracy required 
varies. The piece is held in a vise, and the method of working is to 
grasp the chisel firmly with the left hand, holding the cutting edge 
to the work and striking the head of the chisel with the hammer, 
keeping the eyes on the edge of the chisel to watch the progress of 
the work. Fig. 47. The lower side, or bevel of the chisel, is the guid¬ 
ing surface and is held at a very slight angle w T ith the finished portion 



Fig. 47. Bench Chipping 


37 





28 


MACHINE SHOP WORK 


of the work, the cutting edge only touching. Raising or lowering 
the shank of the chisel increases or decreases the inclination of the 
guiding bevel and causes the chisel to take a heavier or lighter cut. 
If the hand is carried too low, the chisel will run out before the end 
of the cut; while if the hand is raised too high, the progress will be 
slow, owing to the resistance offered by the metal to separation. 
The depth of the cut taken with a cold chisel should never be more 
than an eighth of an inch. 

^ hen chipping wrought iron or steel, a piece of waste saturated 
with oil should be kept on the bench and the edge of the chisel fre¬ 
quently thrust into it. This lubricates the surfaces in contact and 
preserves the cutting edge of the chisel. While lines are used as 
guides in chipping operations, it is never advisable to bring the 
surfaces too near them with the chisel; sufficient stock must be left 
so that the surfaces may be finished with a file. This is especially 
to be observed in chipping keyways with a cape chisel; an ample 
margin for filing should be left both on the sides and on the bottom. 

FILES 

Characteristics. The file differs from the chisel in having a 
large number of cutting points instead of one cutting edge and in 
B a 



Fig. 48. Hand File 

being driven directly by the hand instead of by the hammer. As 
hand power only is used, it is evident that the amount of metal 
removed at one stroke will be small, and the amount removed by a 
single tooth will be exceedingly small. 

Files are made from cast or crucible steel and in manufacture 
pass through the successive processes of forging, annealing, grinding, 
cutting, hardening, and tempering. They have three distinguishing 
features length, kind or name, and cut or coarseness of teeth. 
Length is measured from the heel A to the point B, Fig. 48, the tang 
C not being included. These lengths vary from 3 inches to 20 inches. 

Classification of Style and Cuts. There are many kinds of files 
manufactured. Those in common use are shown in section in Fig. 49 


38 





MACHINE SHOP WORK 


29 


as follows: A —flat file; B —hand file; C —warding file; D —square 
file; E —three square or triangular file; F —half round file; and 
G —round file. 

The cut of files is in two styles—single and double; and each 
style has several grades of coarseness, viz, coarse, bastard, second- 



n b 


B 

D e: r 

Fig. 49. Cross-Section of Files 



Ewwmi 

c 



cut, smooth, and dead smooth. The last two grades are some¬ 
times called fine and superfine. As is shown in Fig. 50, the coarse¬ 
ness of each style varies with the.length—the longer the file the 
coarser the cut. 

Convexity of Files. If the cutting surface of a file were perfectly 
flat, the number of teeth or cutting points engaged with the work 
would depend on both the 
width of the file and the 
width of the piece being filed. 

To force as many cutting 
points as would be contained 
in such a large area deeply 
enough into the metal to 
enable each to remove its 
share of the stock would be beyond the power of the man pushing 
the file. To avoid this necessity for great pressure, files are usually 
“bellied” or made slightly convex in the direction of their length, so 
that, theoretically, the file and the work are in contact only on a 
line as long as the width of the file. This enables the file to be 
forced into the metal sufficiently for the teeth to bite, and thus 
avoids dulling the teeth, which always occurs when the file is 
allowed to glide over the work without sufficient cutting. 



Fig. 50. Diagram Showing Coarseness of Files 


39 

















30 


MACHINE SHOP WORK 


This convexity of files also serves another purpose. The pres¬ 
sure applied to the file to make it bite bends the file more or less, 
Fig. 51, and if the file in its natural state were perfectly flat, when 
cutting it would be concave; and this would prevent the production 



Fig. 51. Bench Filing 


of a flat surface as it would cut away at the edges of the work, leav¬ 
ing a convex surface. Such files might, however, be used on convex 
surfaces. 

Height of Work for Different Classes of Files. Work for filing 
is usually held in a vise, and, under ordinary circumstances, the 




Fig. 52. Special File Holder 


surface of the work should be about the height of the elbow. For 
fine work with small files, where close observation is of more impor¬ 
tance than pressure on the file, the work should be higher than this, 


40 





















MACHINE SHOP WORK 


31 


the height increasing with the refinement of the work. On the 
other hand, for very heavy filing, where great pressure is absolutely 
necessary, the work should be several inches below the point of the 
elbow, so that the weight of the body may be used to good advantage, 
and also because the workman naturally stoops a little when exert¬ 
ing a great pressure on the file. 

File Handles. The handles commonly attached to files are of 
wood and are made to fit the hollow of the hand. The handle is 
driven onto the tang of the file, a 
ferrule on the handle preventing 
it from splitting. Care should be 
taken to have the axis of the 
handle parallel with the file. A 
good way to prepare the handle for 
the tang is to heat the tang to a 
dull red, the file proper being kept 
cool by a piece of wet cotton waste, 
and the hole in the handle burned 
out until the tang is almost in the 
position it is designed to finally 
occupy. After cooling the tang, 
very little driving will be required 
to securely fasten the handle to 
the file. 

When filing surfaces of such 
size that the handle as ordinarily 
applied would interfere with the 
use of the file, the tang may be 
bent up to an angle so that the 
handle will clear the surface. Various forms of holders are used 
for filing under these circumstances, the simplest forms being shown 
in Fig. 52. 

Correct Filing Position. The correct position for filing is about 
as follows: feet about 8 inches apart and at right angles, the left foot 
being in line with the file; stand back from the vise so that the body 
may follow the file slightly; grasp the file handle with the right hand, 
fingers below, thumb on top of, the handle. For coarse filing, place 
the ball of the thumb of the left hand on the point of the file, and for 



Fig. 53. Bench Filing Position 


41 






32 


MACHINE SHOP WORK 


fine filing grasp the point of the file with the thumb and forefinger 
of the left hand, Fig. 53. When holding the file in one hand, as is 
often done in light work, the forefinger should be on top of the file, 
pointing in the direction of its length, as is shown in Fig. 54. This 
allows free movement of the hand and wrist, pressure being applied 
principally by the forefinger. 

As file teeth or cutting edges point toward the end of the file, 
it is evident that the file can cut only when moving in a forward 
direction. On the return stroke, the pressure should be relieved; 
otherwise the teeth will be dulled when drawn back over the surface. 

Choice of Files Depends on Work. The kind of metal being 
worked determines in a great measure the character of the file to be 
used. Cast iron, especially if the scale has not been previously 
removed, is particularly hard on a new file, as the glassy character 



of the scale tends to dull the cutting edges. New files should never 
be used on such a surface. It is found that on tool steel, and on hard 
materials generally, a second-cut file is better than the bastard. 
This is because if pressure enough is exerted to cause the coarse 
teeth of the bastard to bite into the work, the teeth, being com¬ 
paratively long, are very likely to be broken off. In the second-cut 
file, the teeth are shorter and present more cutting points in a given 
area, thus preventing excessive duty being imposed on a few teeth. 

Softer metals, such as brass and bronze, allow the use of the 
coarser grades. 

Cleaning File. The particles of metal removed by a file fre¬ 
quently remain in the teeth and diminish their cutting qualities. 
In the case of hard metals, these particles, or “pins”, often scratch 
the work. It is necessary, therefore, that files be frequently cleaned. 
This may be done in a measure by striking the edge of the file lightly 


42 






MACHINE SHOP WORK 


33 


against the bench or vise, but it is more effectually performed by 
using a stiff brush or a piece of card clothing, Fig. 55. In the finest 
grades of files, a thin piece of wood or sheet brass may be drawn 
across the surface of the file as shown in Fig. 56, and the filings are 
removed by the points 
extending into the file 
teeth. 

When filing cast 
iron, neither the file nor 
the work should be 
allowed to become greasy, 
as this tends to make 

the file slide Without Fig. 55. Removing Pins from a File 

cutting. In filing steel, 

however, if the file be oiled or filled with chalk, the pinning of 
the file is prevented in a large degree, and frequent use of the card 
or brush is not necessary. 

Draw Filing. What is known as draw filing is done by grasping 
the file at each end and moving it sidewise across the work, Fig. 57. 
The amount of stock removed by this process is usually very small, 
the object being to lay the file marks parallel to the length of the 
work. For draw filing, single-cut files are better than double-cut 
as they are less likely to scratch the work. The remarks concerning 
cleaning, oiling, and chalking apply both to cross filing and draw 
filing. 

Polishing. No matter how carefully filing is done, it does not 
leave a surface that is pleasing to the eye; the file marks are more or 




Fig. 56. File Brush 


less irregular and the whole surface is dull. Exposed parts of 
machines which are not painted are usually polished. Polishing 
does not necessarily improve the surface, but simply brightens it 
and renders it more attractive. As a rule, a polished surface is not 
a true surface, no care being taken to maintain its trueness. In 


43 





34 


MACHINE SHOP WORK 


ordinary machine work, polishing is usually done by abrasives, such 
as emery, corundum, and carborundum; while rouge, crocus, rotten- 
stone, and tripoli are used on fine work, especially on brass and 
composition. Emery, for example, is crushed and sorted into 
grades varying from No. 8 to flour, the number of the grade indi¬ 
cating the number of meshes per linear inch in the sieve used in 
sorting. These grades sometimes bear arbitrary designations. No. 1 
indicating a coarse grade and Nos. 0, 00, 000, 0000 showing the finer 
grades. 

Methods of Using Powders and Cloths. Emery powders are 
sometimes mixed with oil and applied directly to the work by 



Fig. 57. Draw Filing 


wooden blocks or clamps; but the more common method is to use 
what is known as emery cloth, the grains being glued to a strong cloth 
backing. The finer grades are used on paper in the same manner. 

Emery cloth is used in many ways—it may be wrapped around 
a file; folded or tacked to a block of wood; glued to wooden sticks 
about 15 in. X 1^ in. X \ in., fastened around rollers for internal 
curves, or glued to wooden or steel discs and rotated in a lathe or 
special machine. In all cases the object is to grind down the sur¬ 
face, using a sufficient number of grades of cloth to produce the 
degree of polish desired. The marks are laid parallel to each other, 
making what is known as a “grain”. When the process is to be 
carried to such an extent that no grain is to be visible, the finer 


44 








MACHINE SHOP WORK 


35 


polishing agents are used, usually applied with a cloth wheel or 
“lap”. Old cloth does finer work than new, and oil on the cloth will 
make a finer cut. 

Hand Scraping. When two flat or curved surfaces are to be 
worked together, and close contact over the surfaces of both is 
desired, they are hand scraped. Scraping removes less metal than 
filing and also enables the workman to confine the removal to limited 
areas. The scraper, which should be made from a very close- 
grained tool steel, is nearly 2 feet long exclusive of the handle. The 
general shape is shown in the upper view of Fig. 58. The cutting 
edge is about ^ of an inch thick and 1| inches wide. It is ground 
on an emery wheel or grindstone and carefully oilstoned, leaving the 
cutting edge as straight as possible. Scrapers are sometimes made 
from old files, the teeth being ground off and the end drawn out 




Fig. 58. Straight and Bent Hand Scrapers 


wide and thin. Sometimes the end is bent at right angles to the 
shank, as shown in the lower view of Fig. 58. The cutting done by 
scrapers should be perfectly smooth and free from scratches. 

Testing Plane Surfaces. In using the surface plate as a test for 
the trueness of a plane, such as a valve or its seat, the plate is 
covered with a very thin coating of red lead and then rubbed over 
the valve or seat. The latter should have previously been finished 
as smoothly as possible. The spots where the red lead shows contact 
are scraped off and the process continued until contact over the 
entire surface is obtained. During the last part of the operation, 
alcohol should be used instead of red lead, as it leaves clean bright 
spots to indicate where the scraper must be applied. Small pieces 
of work are rubbed over the surface plate, and in any case care 
should be taken to distribute the wear uniformly over the plate in 
order to prolong the trueness of the plane. The scraper for concave 


45 

































36 


MACHINE SHOP WORK 


surfaces, such as boxes, is of the general shape of a half-round file 
without teeth. In such cases, the shaft to be used takes the place 

of a surface plate. The method of 
holding and using such a scraper is 
shown in Fig. 59. 

Scraping for Finish Only . 
Scraping is sometimes done as a 
matter of finish, and not for the 
purpose • of getting an accurate sur¬ 
face. It is then termed “spotting”. 
A spotted surface, therefore, does 
not always indicate accuracy. Many 
machine parts can be more cheaply 
Fig. 59 . Scraping spindle Bearing finished by scraping than by polishing. 

HAND PUNCHES 

Prickpunch. The prickpunch. Fig. 60, is made of cast steel 
with a hardened conical point of about 60 degrees. It is about 3J 
inches long and \ inch in diameter. It is used for making very small 
indentations at intervals of about \ inch on a line. 

Center Punch. The center punch, also shown in Fig. 60, is 
made of the same general appearance as the prickpunch, but is 





Fig. 60. Hand Punches. Forged Center Punch Above; Prickpunch Below 

about 5 inches long, J inch in diameter, and has a point angle of 
about 90 degrees. The principal use of this punch is to make center 
holes, marking the centers on the ends of pieces to be turned. 

Ordinary forged center punches are usually made of hexagonal 
steel; but if round stock is used, the grip should be fluted or knurled 
to prevent slipping in the fingers. 


46 

















MACHINE SHOP WORK 


37 


Scratch Awl. The scriber or scratch awl, Fig. 61, is made in 
many forms, but consists essentially of a cast-steel rod about 8 
inches long and inch in diameter, with a long, slender, hardened 





N0.67. 



Fig. 61. Forma of Scribera 

Courtesy of L. S. Starrett Company, Athol, Massachusetts 


point at each end. Frequently one point is bent at right angles to 
the shank. As the name indicates, this tool is used for marking 
lines on the surface of metal. 


TEMPLETS 

Where the same lay-out is to be many times repeated, templets 
are used. This method avoids the necessity of making measure¬ 
ments in the laying out of the work. 

Marking Templet. The marking templet consists of a piece 
of the same shape as the finished article. It is usually laid on a flat 



Fig. 62. Steel Clamps 


surface and held fast by iron clamps as shown in Fig. 62. The out¬ 
line is then marked on the surface with a scriber and sometimes 
emphasized by prickpunch marks. 


47 





































38 


MACHINE SHOP WORK 


Filing Templet. The filing templet is of the same character as 
the marking templet except it is hardened. It is clamped in the 
vise with the piece to be shaped, and the surface filed down to coin¬ 
cide with the form of the templet. 

Jigs. Where holes are to be drilled in duplicate, a templet 
known as a jig is used. These jigs are made so that they fit over 
the piece to be drilled and, when clamped in position, indicate the 
location of the holes by means of hardened steel bushings set in the 
templet. 

The making of templets and jigs is one of the finest branches of 
the machinist’s work and is generally classed under the head of “Tool- 
Making”. The rapid and economical production of machine parts 
in quantity depends largely on the tool-maker, who must, therefore, 
be considered the highest type of machinist. 

DRILLING 

Drilling. Drilling is the term used by shop men to denote hole 
production by means of a rotating tool which is provided with 
cutting edges located at its poipt. The drill, therefore, is an end 
cutting tool as distinguished from the ordinary reamer which usually 
cuts on its sides. 

Types of Drills 

Flat Drills. Drills are of two general classes, the flat and the 
twist. A flat drill of a common type is shown in Fig. 63. The 
angle between the two cutting edges should be about 110 degrees. 
These drills are usually made from round tool steel drawn out wide 
and thin, as shown, the undressed end being used for holding. The 
flat drill is usually made in the shop where it is to be used. Its low 
first cost is the principal reason for its existence. 

Flat Chucking Drill. Flat drills made from thin flat stock are 
used in connection with a slotted rest to start and drill holes in the 
lathe without previous centering. They are called chuck drills. 
The end of the shank of the drill is provided with a center hole to 
receive the dead center of the machine. The drill and rest are 
shown in Fig. 64. 

Twist Drills. The simplest form of twist drill is cylindrical 
throughout its entire length, as shown in Fig. 65, and has two spiral 
flutes which at the end serve to form the cutting lips, and which also 


48 


MACHINE SHOP WORK 


39 


serve to carry the chips from the hole. The included angle of the 
lips is 118 degrees. The twist drill will work more accurately than 
the flat drill, as the cylindrical portion serves as a guide to keep the 
cutting lips in their proper position. The edge, being somewhat 



Fig. 63. Blacksmith’s Drills 


hooking, removes the metal by a cutting instead of a scraping action 
as in the flat drill. This form of drill not only can be fed faster but 
can be forced into the work with less power, as it has a tendency, 
especially noticeable in soft metals, to feed itself into the work. 
Straight shank twist drills 
are made from .0135 inch to 
inches in diameter; the 
smaller sizes are sold in sets 
designated by the numbers 1 
to 80; by the letters A to 
Z; or by the fractional sizes 
| inch to yq inch. 

Tapered Shanks. The 
taper-shank twist drill is 
shown in Fig. 66. It con¬ 
sists of a body A , which is fluted and does the actual work, and 
a taper shank B, by which it is held. This taper fits accurately 
into the spindle or chuck of the drill press. At the end there is a 
tongue C, which slips into the keyway in the spindle or chuck. As 


C 


mms 


i-1 _ d|-1 

i i i 

I rp-*-»—n I 

I_ 


Fig. 6 


Chucking Drill Rest 


49 























































40 


MACHINE SHOP WORK 


this surface is flat, it serves as a bearing by which the drill is driven. 
This relieves the tapered portion from the stress of driving by fric¬ 
tional resistance alone. For small drills this frictional resistance is 
sufficient, but for larger sizes it will not do at all. If for any reason 
the tongue should become broken, no dependence should be placed 
upon the frictional resistance of the taper shank to drive the drill. 



Fig. 65. Typical Twist Drill 

Courtesy of Union Twist Drill Company, Athol, Massachusetts 


The drill will slip and wear the socket, which will become enlarged 
and make a misfit for other drills. 

The standard taper for drill shanks, known as the Morse, is 
| inch to the foot. There is another standard taper, known as the 
Jarno, which has a taper of to inch to the foot. No attempt should 
be made to run the drills of one taper in the sockets of the other. 



Fig. 66. Taper Shank Twist Drill 

Courtesy of Morse Twist Drill Company, New Bedford, Massachusetts 


A flat taper key, or drift, introduced into the keyway, engages 
the end of the tongue and serves to remove the drill from the spindle. 

Farmer Drills. Drills of cylindrical form are also made with 
straight flutes as shown in Fig. 67. They are used for drilling soft 
metals, such as brass, especially when the drill passes entirely through 



Fig. 67. Straightway or Straight Fluted Drill 
Courtesy of Union Twist Drill Company, Athol, Massachusetts 


the piece. As it breaks through the metal, a drill with spiral flutes 
tends to draw itself through rapidly, as if it were a screw working 
in a nut. This may break the drill or move the work from position. 
Straight flutes give the same cutting action as a flat drill and avoid 
the tendency to draw. 


50 





MACHINE SHOP WORK 


41 


Care of Drills 

Lubrication of Drills. When drilling tougn metals, such as 
steel and wrought and malleable iron, heat is generated by the 
bending or changing of the form of the metal being removed and by 
friction caused by the chips moving over the lips of the drill. The 
heating is similar to the heating of a piece of wire bent quickly back 
and forth. As there is danger of heating the drill to a temperature 
that will draw the temper and soften the drill, plenty of lard oil, or a 
mixture of potash and water, should be used. This is not so much 
for lubrication as to remove the heat. 

Copper is the most difficult to drill of all the common metals on 
account of its extreme toughness; then, too, copper h^ats to a higher 
temperature on account of its low specific heat. Brass does not 
require the use of oil, and cast iron is usually drilled dry. 



Fig. 68. Oil Tube Drill 


As the heat is produced at the point of the drill, it is desirable, 
particularly in the case of deep holes, that the oil be applied directly 
at the drill point. For this purpose, oil-tube drills, such as shown 
in Fig. 68, are used. The oil is supplied under pressure, and not 
only removes the heat but also carries away the chips. 

Speed of Drills. The speed at which drills should be rotated 
depends both on the diameter of the drill and on the material oper¬ 
ated upon. No absolute rule can be given for any one metal or 
diameter of drill because of the variation in hardness and tenacity of 
the material and the condition of the cutting edge of the drill. The 
operator must exercise his own judgment. 

Table I, giving the speed of drills in revolutions per minute, is 
based on a peripheral speed of 30 feet a minute for mild steel, 35 
feet per minute for iron, and 60 feet per minute for brass, using 
carbon tool [steel drills. 

The rate of feed also depends on the drill diameter and on the 
material. The Cleveland Twist Drill Company gives, as a maxi¬ 
mum, one inch of feed for 95 to 125 revolutions. 


51 


42 


MACHINE SHOP WORK 


TABLE I* 
Speed of Drills 


Diameter 
op Drill 

Soft Steel 
or Wrought Iron 
< r. p. m.) 

Cast Iron 
( r. p. m.) 

BRA8S 
(r. p. m.) 

i 

is 

1824 

2128 

3648 

l 

8 

912 

1064 

1824 

_ 3 _ 

16 

608 

710 

1216 

1 

4 

456 

532 

912 

5 

16 

365 

425 

730 

3 

8 

304 

355 

608 

xf 

260 

304 

520 

1 

2 

228 

226 

456 

-16 

203 

236 

405 

5 

8 

182 

213 

365 

11 

16 

166 

194 

332 

f 

152 

177 

304 

ft 

140 

164 

280 

7 

8 

130 

152 

260 

15 

16 

122 

142 

243 

1 

114 

133 

228 

1* 

108 

125 

215 


102 

118 

203 


96 

112 

192 

H 

91 

106 

182 


87 

101 

174 

if 

83 

97 

165 

ll6 

80 

93 

159 

. H 

76 

89 

152 

Iff 

73 

85 

145 

H 

70 

82 

140 

1 16 

68 

79 

135 

If 

65 

76 

130 

Itt 

63 

73 

125 

Iff 

60 

71 

122 

59 

69 

118 

2 

57 

67 

114 


Resharpening Drills. Great care should be exercised in the 
resharpening of drills. The cone point of a drill should be symmetri¬ 
cal, that is, the lips should be of the same length and form the same 
angle with the axis. If the lips are of unequal length, the hole will 
be larger than the drill, as is shown in Fig. 69. The point is not in 
the axis, and the hole will not only be large but also will not be 
parallel to the drill spindle. If the lips do not form equal angles 
with the axis, all the cutting will devolve upon the one making the 
greater angle, as shown in Fig. 70. Such a drill will not cut as 
fast as, and will become dull sooner than, one which is properly 
ground. 

♦Courtesy of Cleveland Twist Drill Company. 


52 










MACHINE SHOP WORK 43 

Hand-grinding, especially of twist drills, is neither accurate 
nor satisfactory; it is much better to do such work on a regular drill 
grinder built especially for the purpose. 




When resharpening carbon tool steel drills, care must always 
be exercised that the cutting edge is not overheated on the stone 
or emery wheel. If it is overheated, the temper will be drawn and 
the drill become too soft to 
properly do its w r ork. The 
clearance angle is also of 
extreme importance. This 
should be 12 degrees, as 
shown in Fig. 71. If the drill 
lips are not properly cleared 
or backed off, the drill must 
crush. 



Fig. 71. Cutting Edge Clearance 


REAMERS 

Use of Reamers. It is difficult, if not quite impossible, to drill 
a hole to an exact nominal diameter. For much work, a variation 
of a few thousandths of an inch from the nominal diameter is of no 
account. Where greater accuracy than this is required, the holes 
are reamed, that is, the hole is first drilled somew T hat smaller than it 
is desired and is then reamed out to the proper size with a reamer. 


53 

























44 


MACHINE SHOP WORK 


Holes drilled with the flat chucking drill are usually yg- inch 
under the finish size. A flat chucking reamer, Fig. 72, is used to 
enlarge the hole to within about .005 inch of the true size. This 
reamer is centered on both ends and turned to size. The entering 



end, which does the cutting, is given a short, sharp taper, while the 
straight portion serves as a guide to keep the tool in position. By 
this means, the drilled hole is straightened and brought close to size. 

Hand Reaming. To give the hole a smooth surface and a cor¬ 
rect diameter, a fluted hand reamer, of which there are various forms, 
is used. This tool is not intended to remove large amounts of 
metal, but serves only to increase the size of a hole by a small frac¬ 
tion of an inch up to the diameter required. The hole should not 
be more than 0.007 inch smaller than the hand reamer. It is evident 
that if the reamer were to be made of the same diameter throughout 
its whole length, it would be very difficult to make it enter the hole. 
In order to facilitate this, it is usually made slightly tapering for a 
distance from the entering end equal to about one diameter. 

One form of reamer has a shallow screw thread cut at the enter¬ 
ing end. This thread takes hold of the metal and draws down into 
the work. When using a reamer, it is always well to pass the entire 



Fig. 73. Solid Hand Reamer 


tool through the hole. The leading end is subjected to the greatest 
amount of wear because it does the greatest amount of work. If, 
therefore, only the leading end is put through, the hole will not be 
of a uniform diameter throughout. Oil should always be used on 
reamers when they are working in wrought iron or steel. 

4 he hand reamer, Fig. 73, is the typical form, and one which 
can be used in many cases in place of special forms. Fig. 74 is better 


54 





















MACHINE SHOP WORK 


45 


adapted for use in the lathe than the hand reamer. This may 
follow the flat chuck reamer to finally finish a hole. 

In reaming cored holes, the cylindrical chuck reamer, some¬ 
times called a roughing reamer, is often used. It is made either 



Fig. 74. Plain Shell Reamer Fig. 75. Rose Shell Reamer 

Courtesy of Brown and. Sharpe Manufacturing Courtesy of Brown and Sharpe Manufacturing 
Company, Providence, Rhode Island Company, Providence, Rhode Island 

rose, Fig. 75, fluted, or with three spiral flutes, Fig. 76, and generally 
has solid shanks. The last-named style will finish very smooth and 
close to size when started true by preliminary boring. 



Fig. 76. Spiral Chucking Reamer Drill 


A solid reamer cannot be sharpened without reducing its diam¬ 
eter; therefore, it must be used carefully in order to prolong its life. 
Reamers with adjustable blades meet this objection, but cost much 




Fig. 77. Expanding Reamer and Arbor 


more than the solid form. An expanding reamer, Fig. 77, can be 
slightly enlarged to compensate for grinding and is then used as a 
solid reamer. Fig. 78 shows an adjustable reamer with inserted 
blades. 


55 


























































46 


MACHINE SHOP WORK 


Taper Reamers. Reamers are made for tapered as well as for 
straight holes. The angle varies with the intended use of the taper. 
For example, the locomotive taper of inch per foot is intended for 
bolt holes where plates are to be drawn solidly together and the 



Fig. 78. Reamer with Inserted Blades 

Courtesy of Brown and Sharpe Manufacturing Company , Providence, Rhode Island 

holes completely filled. It is very difficult to remove a bolt from a 
hole with such a slight taper. When pieces are pinned together, 
such as a hub to a shaft, it is intended that they can be separated 
when desired, so the taper is made steeper, generally \ inch per foot. 




Fig. 79. Types of Taper Reamers 

This has come to be known as the pin taper. Taper holes for holding 
lathe centers and taper shank twist drills are generally made f inch 
per foot —the Morse taper. This angle holds the tool firmly, and still 
it can be easily removed. The three tapers mentioned are recog¬ 
nized as standard, and 
reamers for them are car¬ 
ried in stock. Of course 
many other tapers are used 
by different manufacturers, 
but they are regarded as 
special. Fig. 79 shows taper 
reamers. 

Taper reamers differ from hand reamers only in the angle and 
by not requiring the tapered entering end. 

Holes to be reamed by taper reamers must be slightly larger 
than the small end of the reamer; and, if the hole is deep, it is usual 



56 

































MACHINE SHOP WORK 


47 


to make a stepped hole, shown exaggerated in Fig. 80, by using 
drills of different diameters. 

When not carefully sharpened, all forms of reamers have a 
tendency to chatter and produce rough surfaces. To avoid this, 
the flutes are frequently irregularly spaced; another method is to 
use spiral flutes, usually left hand. 

HAND THREADING TOOLS 
Taps 

Types of Taps. When internal thread cutting is done by hand, 
the tool used is called a tap. There are many styles of taps, the 



Fit? 81 Types of Hand Taps: Left—Taper Tap; Center—Plug 
Tap; Right—Bottoming Tap 
Courtesy of Wiley and Russell Manufacturing Company, 

Greenfield, Massachusetts 

names in some cases being suggested from the shape, but more often 
from the use. In most machine shops are found the following 
forms: hand, machine screw, pipe, pulley, stay-bolt, boiler, and 
tapper; of these the hand and machine screw are the most common. 
The object of all is to make helical grooves, called threads, m holes, 
so that they may receive and hold screws, bolts, studs, etc. 

Size of Drill for Tapped Hole. As the size of a tap is the out¬ 
side diameter of its threads, it is evident that the hole drilled for 


57 












48 


MACHINE SHOP WORK 


TABLE II 

Taps and Corresponding Drills 


Tap 

Diameter 

(in.) 

No. 

Threads 
( per in.) 

u. s. 

Standard 

Drill 

Diameter 

(in.) 

V-Thread 

Drill 

Diameter 

(in.) 

Tap 

Diameter 

(in.) 

No. 

Threads 
( per in ) 

u. s. 

Standard 

Drill 

Diameter 

(in.) 

V-Thread 

Drill 

Diameter 

(in.) 

1 

20 

A 

H 

If 

5 

If 

Iff 

T6 

18 

4 

64 

2 

41 

1 23. 

A 32 

m 

3 

8 

16 


T 2 

21 

41 

Iff 

if 

7 

16 

14 

If 

H 

21 • 

4 

2A 

2& 

1 

13 

11 

32 

If 

2f 

4 

2ts 

2H 

16 

12 


16 

3 

31 

2f 

21 

8 

11 

1 

1 

3f 

31 

2f 

21 

if 

11 

VS 

ft 

31 

31 

31 

2ff 

4 

10 

8 

if 

3f 

3 

3 -h 

3^ 

H 

10 

H 

21 

32 

4 

3 

3 

3fir 

1 

9 

s 

45 

64 

41 

21 

3M 

3R 

15 

16 

9 

3 

4 

49 

64 

41 

2f 

4 

3f 

1 

8 

27 

32 

13 

16 

4f 

2f 

41 

41 

^16 

If 

7 

15 

16 

29 

32 

5 

21 

41 

41 

1? 

7 

1 16 

1^2 

51 

21 

41 

41 

If 

6 

1 h 

H 

51 

2f 

5 

4f 

U 

6 

IsT 

Iff 

5f 

2f 

51 

5 

If 

5f. 

H 

llT 

6 

21 

51 

51 

If 

5 

ll 

Iff 





tapping must be smaller than the tap by nearly, if not quite, twice 
the depth of the thread. The shape of the thread partly determines 
the amount to be subtracted from a tap diameter. There are now 
recognized as standard, five different threads—sharp or V; Franklin 
Institute or United States standard; Whitworth; International or 
metric; and the 29 degrees or Acme. These shapes will be described 
and compared under “Screw Cutting”. Table II shows the diam¬ 
eters of the holes that are to be drilled for cutting the various sizes 
of the threads according to the United States standard and the 
ordinary V-thread. 

Hand taps are most commonly used in shop practice, and a 
description of their operation will answer for all styles. They are 
usually sold in sets of three—taper, plug, and bottoming—Fig. 81. 

Hand Tapping. The cutting of a thread with a tap is not a 
difficult operation but requires care in the manipulation. The tap 
does not need to be forced into the work, since the thread will draw 
it forward. The tapering of the tap has a two-fold effect. No one 
thread does all of the work in the removal of the metal; each succeed¬ 
ing thread removes a small amount until the full thread has entered 


58 















MACHINE SHOP WORK 


49 


the hole. The second effect is that, as in the case of a reamer, the 
tap is easily entered and started. Care must always be exercised 
at this point of the work. The taper of the tap allows it to easily 
enter the hole and also makes it possible for it to enter at an angle. 
If it is started in the latter condition, the thread will not be at right 
angles to the surface. The degree of care needed in the starting of 
the tap depends upon the job that is to be done. In the case of tap¬ 
ping a nut, it will usually be quite sufficient to set the tap by the 
eye. In finer classes of work, however, the tap should be set with a 
square. Start the tap into the hole and place a square on the sur¬ 
face beside it in two positions at right angles to each other and see 
that the tap stands parallel to the vertical blade. 

Starting the Tap. When holes have been drilled that are to be 
tapped, a good way of setting the tap is to put a center in the drill 
spindle. Put the tap into the hole and bring this center down into 
the center hole in the head of the tap; this will steady the latter 
while it is being started. 

In using the tap, it is well to work it back and forth. This 
allows the chips to work clear of the cutting edges, and the oil to 
cover them. In case of heavy work, it is possible to drive the tap 
with the drill spindle, but when thus driving a tap in a machine, 
the backing up is impossible. 

Use of Bottoming Tap. Sometimes a thread is to be cut down 
to the bottom of a hole that does not pass entirely through the metal. 
In this case the bottoming tap is used. This is a tap that is not 
tapered at the entering end. The method of working is to first cut 
the thread as far as possible with the plug tap and then use the 
bottoming tap, which will enter easily and can be driven to the 
bottom. 

Machine Tapping. Machine tapping is best done by using a 
frictional tapholder, that is, one in which the friction is enough to 
cut the threads, but which will slip when the tap strikes the bottom 
of the hole. This will insure the hole being tapped to the bottom 
and avoid all danger of breaking the tap. To withdraw the tap, the 
machine is reversed, usually at a higher speed than used in tapping. 

Lubrication. When tapping wrought iron and steel, a plentiful 
supply of lard oil should be used. On brass the use of oil is unneces¬ 
sary, and cast iron may be tapped dry. 


59 


50 


MACHINE SHOP WORK 


Threading Dies 

Dies are used for cutting threads on bolts and other similar 
parts to be placed in holes which have been threaded by taps. The 
general rules given for the use of taps apply to dies. As the number 
of threads in a die is much less than on a tap, and because the 
chips have a much freer exit, it is not 
as necessary to back up a die as it is 
a tap. 

Solid Dies. Dies for small work are 
usually made solid, as shown in Fig. 82, 
and often have a slight adjustment for 
altering the size. They cannot be sharp¬ 
ened, but have an advantage in readily 
centering on the work. As the full thread 
is cut at one passage of the die, it takes 
considerable power to operate solid dies of 
large size. For this reason, hand-operated solid dies are seldom used 
above one-half inch. The holder or die stock shown in Fig. 83 has 



Fig. 82. Threading Die 




a guide to hold the work at right angles to the die, but die stocks 
are often made without this convenience. 

Split Dies. The split form of die, generally known as the 
jamb-die. Fig. 84, can be easily resharpened, has unlimited adjust¬ 
ment for size, and cuts the thread by easy stages, as it were. It is 


60 











MACHINE SHOP WORK 


51 


made in sizes up to 2 inches and is for hand operation only. The 
holder for this form of die is called a screw plate, Fig. 85. These 
are not furnished with guides for the work. 

Cutting Pipe Threads, Another common form of thread 
cutting is that on wrought-iron pipe. The pipe thread is rounded 
slightly at top and bottom and is 
made tapering at the rate of 
three-quarters of an inch per 
foot. The dies are usually solid, 
square in form, and the die stocks 
are provided with a ring which 
fits over the pipe and serves to 
hold it square with the die. This 
avoids the danger of cutting 
the thread at an angle with the 
pipe axis. 

Comparatively little thread cutting is done by hand, a large 
proportion of all such work being performed on bolt-cutters. This 
is ordinarily the roughest and cheapest class of work, and the run¬ 




ning of the bolt-cutter is often the first work to which the apprentice 
is assigned. 

Cutting Bolt Threads. An ordinary type of bolt-cutter is 
shown in Fig. 86. The dies are held in the head A. Instead of 
being solid, as in Fig. 82, they are made in sections and can be opened 
or closed by the movement of the lever B. A chuck C is placed on 
a traveling head, and this can be moved back and forth by the hand- 


61 



























52 


MACHINE SHOP WORK 


wheel D . The method of working is very simple. The dies in the 
head are closed in order to be in the working position. The bolt to 
be cut is gripped in the chuck by turning the handle E and forced 
against the dies by the handle D. As soon as the dies have taken 



Fig. 86. Bolt Cutter 


hold, they draw the bolt ahead. When a sufficient length of thread 
has been cut, the dies are opened and the bolt withdrawn. This 
avoids the necessity of backing out, as would be required if the dies 
were solid. While the thread is being cut, the dies are kept flooded 
with oil. 


62 












































HISTORICAL DEVELOPMENT OF HARTNESS FLAT TURRET LATHE 

Courtesy of Jones and Lamson Machine Company , Springfield, Vermont 




















MACHINE SHOP WORK 

PART II 


POWER=DRIVEN TOOLS 

LATHES 

Origin. The lathe is undoubtedly the oldest form of machine 
tool. Its prototype is the drilling machine. Each of these machine 



tools probably developed from that earliest example of mechanical 
rotary motion of which we have a record, the “potters’ wheel”. 

Speed Lathes. This term includes that line of lathes illus¬ 
trated in Fig. 87, which shows a typical design. These machines 


65 




























54 


MACHINE SHOP WORK 


are sold in the open market in a variety of sizes from the smaller 
jewelers’ lathe to those having a swing of 12 inches. All types 
and all sizes are designed to be used with hand-controlled cutting 
tools, and are often designated as hand lathes. If desired, they can 
be driven by foot power and are then often termed foot lathes. 

Tools for Hand Turning. In turning brass and composition 
the tools cut by a scraping action, and are almost always held at 



Fig. 88C. Round Nose 
Fig. 88. Cutting Tools for Hand Turning 


or below the center. The three tools shown in Fig. 88, called the 
planisher, graver, and round nose, are typical of all the tools neces- 
sary for turning brass, etc. The manner of holding these tools in 
connection with the T-rest is illustrated by the planisher in Fig. 89. 
Fig. 90 shows another view of the T-rest. Typical hand tools for 
cutting iron and steel are the diamond point or graver and the 
round nose, shown in Fig. 91. They are used differently from 


66 



















MACHINE SHOP WORK 


55 


hand tools for brass, in that the cutting edge is carried above the 
center, and the metal is removed by cutting instead of scraping. 

Graver . The graver frequently takes the place of the planisher, 
for it can be used as shown in Fig. 92, either on the outside or on the 




Fig. 90. Simple Hand 
Tool Rest 


end of a piece of work. The graver can be used on brass for a great 
variety of operations; but its use, except in the hands of an expert 
workman, is attended by the danger of catching in the soft metal 
and thus breaking the tool or spoiling the work. 





Fig. 91. Typical Hand Tool for Steel Turning 


Round Nose. The round nose is used solely for turning concave 
surfaces, being held as high on the work as proper cutting will allow, 
as shown in Fig. 93. 


67 

























50 


MACHINE SHOP WORK 


Slide Rest. To make the hand lathe more rapid and more 
certain in operation, it is frequently provided with a tool holder 
called the slide rest, as shown in Fig. 94. This holds the tool rigidly 
and guides it mechanically, so that the work is done more rapidly 
than with the hand tools. Slide rest tools are miniatures of those 



used on larger lathes, hence a description will not be given at this 
point. 

Engine Lathes. This type of machine tool is well illustrated 
by Fig. 95, which shows the common cone belt-driven screw-cutting 
engine lathe of ordinary dimensions. It is commonly sold in sizes 
from 10-inch swing to 30-inch swing. Larger sizes are usually built 

to order. When an engine 
lathe is used for turning, the 
tool is rigidly held in a “tool 
post” clamped to the cross- 
slide, and is not directly hand 
controlled. The modern en¬ 
gine lathe is designed usu¬ 
ally so that by combining a 
direct belt-driven cone and 
suitable back gears a range 
of at least eight rotative 
spindle speeds are obtained. 

The engine lathe illustrated in Fig. 95 has a strong cast-iron 
bed A carried on four well braced legs that may be bolted to the floor, 
though the weight of the machine may be sufficient to hold it in 
position. On the left-hand end of the bed there is fastened the 
headstock B, which carries the main running gear of the machine. 



68 


















MACHINE SHOP WORK 


57 


At each end of the headstock there is a bearing for the spindle. 
Running loosely on the spindle and between the bearing is the cone 
pulley C to which the pinion D is attached. 

Gear Drive . The back gear is designed to reduce the speed of 
the spindle without changing the speed of the belt. The mechanism 
of the back gear is more clearly shown in Fig. 96. The large gear E 
alone shows in Fig. 95. It is driven by the pinion D which is 
attached to the cone. Referring interchangeably to Figs. 95 and 96, 
the pinion on the same sleeve as the gear E drives the gear at the 
right of the cone c. This gear is keyed to the spindle. When the 



Fig. 94. Hand Lathe Slide Rest 


back gear is not in use, it is thrown out of mesh with the gears 
on the pulley and spindle, by means of a shaft having eccentric 
bearings upon which it turns; at the same time the cone pulley is 
fastened to the gear at its right. The spindle then turns with the 
cone pulley. When the back gear is in use the spindle runs more 
slowly, with the belt on the same step of the cone, than it does 
when driven direct. 

Spindle Arrangement. The spindle projects through the bear¬ 
ings at each end. At the right it is usually threaded to receive 
a faceplate F. The spindle is also bored out and tapered at this 
end for a center (7. This center is called the live center because 


69 




58 


MACHINE SHOP WORK 


it turns with the spindle. The dead center II is in the tailstock, 
and hence does not turn. At the left the spindle projects beyond 



the bearings and presses axially against a thrust step. The cone 
pulley I serves as the driving pulley for a narrow belt jrunning to 
the corresponding pulley K on the feed rod N. The pinion J 


70 


Fig. 95. Typical Engine Lathe 
Courtesy of Reed-Prentice Company , Worcester, Massachusetts 





MACHINE SHOP WORK 59 

drives the lead-screw 0 through the intermediate gear M and the 
direct gear L. 

Handling the Work . The work is held on the centers G and H, 
the distance between which is adjusted by moving the tailstock S 
(sometimes called the tailblock). The latter is held to the bed by a 
clamp and bolts tightened by the nuts T. To move the tailstock, 
these nuts are slackened and the stock moved to the proper position. 
The final adjustment is 
made by turning the 
hand wheel Q, which 
rotates a screw in the 
sleeve P. Sleeve P works 
in a nut in the spindle 
of the dead center H, 
which is thus moved in 
and out. When the cen¬ 
ters have been properly 
adjusted and the work 
is in position, the dead 
center is clamped by the 
handle R. 

When work is to be 
turned, the tool is prop¬ 
erly adjusted, and the 
carriage U moved along 
the bed. This move¬ 
ment is accomplished by 
means of gearing, which 
is placed behind the 
apron of the carriage, 
and driven by the shaft N by means of which the cone pulley K is 
keyed. The driving gear meshes with a rack beneath the upper 
ledge of the bed. Connection between the gearing and the shaft 
is made by a friction clutch. The carriage may also be moved by 
hand, by turning the hand wheel V, to which is keyed a pinion 
directly meshing in the rack. 

Tool-Feeding Mechanism. The tool is fed to the work and with¬ 
drawn from it by turning the cross-feed handle W. By means of 



71 




60 


MACHINE SHOP WORK 


the screw and nut, this drives the cross-slide X. This arrangement 
permits any desired transverse or longitudinal position of the tool. 
The motion of the carriage is usually from right to left when at 
work. When screws are to be cut, a different feed is used. In 
ordinary turning, there will be a variation in the relations between 
the rotation of the work and the longitudinal motion of the tool, 
due to the slipping of the belt connecting the cone pulleys I and K, 
or to the slipping of the friction clutch which connects the shaft K 
to the driving gear. To cut a screw-thread, it is necessary that 
there shall be no relative change in the rotation of the work and 
the longitudinal motion of the tool. In other words, the tool must 
travel a given distance for every revolution of the work. To accom¬ 
plish this, the carriage is driven by the lead-screw 0 working in a nut 
set in the carriage. The screw is, in turn, driven by the train of 
gears J, M, and L. The gear J is keyed to the stud. The inter¬ 
mediate gear M runs loose on a sleeve. The gear L is keyed to the 
lead-screw 0. By changing the sizes of the gears used on the stud 
and the screw, any desired thread may be cut. The size of the 
intermediate gear M has no effect on the thread being cut. This 
gear M is used to connect the other two gears L and J and can be 
adjusted to any desired position for that purpose. 

LATHE EQUIPMENT 

Setting Up Change=Gears for Thread=Cutting. The preceding 

descriptions apply particularly to the simple or elementary form 
of engine lathe. The construction of the usual engine lathe is 
somewhat different, and a clear understanding of its essential parts 
is desirable. Instead of being placed directly on the main spindle, 
the first gear J of the train of “change-gears” used for driving the 
lead-screw 0 for thread-cutting, is fixed to the head shaft H, shown 
in B, Fig. 97, upon the inner end of which is fixed the head shaft 
gear G, which engages a gear F of the same diameter fixed to the 
main spindle at the left of the cone pinion D. By this means the 
head shaft II rotates at exactly the same speed as the main spindle. 
The small feed-cone I is fixed to the head shaft II, and the large 
feed-cone K to the feed-rod N, by which ordinary turning feeds 
are produced. 

Referring to the end elevation A in Fig. 97, the change-gears J 


72 


MACHINE SHOP WORK 


61 


and L being of equal diameters and equal numbers of teeth, it 
follows that the lead-screw 0 will revolve at the same rate as the main 
spindle. Therefore, if the lead-screw is cut with four threads per 
inch, the lathe carriage will move a quarter of an inch at each revolu¬ 
tion, and the lathe will cut four threads per inch. 

The intermediate gear M does not change the rate of speed, 
although it reverses the direction of revolution. 

If the change-gear J is only one-half the diameter of the change- 
gear L, the lead-screw 0 will revolve only one-half as fast as the main 
spindle, and therefore the lathe will cut eight threads per inch; but 
if the case is reversed and the change-gear L is only half the diam¬ 



eter of the change-gear J, the carriage will move twice as fast as in 
the first instance, and the lathe will cut two threads per inch. From 
this condition we deduce the rule: 

The thread to he cut will hear the same ratio to that of the lead- 
screw , as the two change-gears hear to each other. 

The ratio will be the same whichever change-gear is the larger. 
It must be remembered, however, that if the change-gear on the 
head shaft is the larger, the resultant thread will be coarser than the 
lead-screw, and vice versa. 

To cut any desired number of threads per inch, we first find the 
ratio which the desired number of threads bears to the number of 
threads on the lead-screw, and then select such change-gears as 
bear this ratio to each other. 


73 





































62 


MACHINE SHOP WORK 


The gears will revolve in the directions shown by the arrows; 
therefore the lead-screw revolves in the direction opposite to the main 
spindle, so that with a right-hand thread on the lead-screw 0 (as is 
usual), the lathe, geared as here shown, will cut left-hand threads. 
If right-hand threads are desired, the intermediate gear M is moved 
to the left, and another gear introduced between it and the gear L. 
An extra stud for this purpose is furnished with each lathe. 

Therefore, it must be remembered that to change from left- 
hand threads to right-hand threads, or. vice versa, we may either 
add one change-gear or take one out, according as the lathe has 

one intermediate gear or two. 

Compounding. When the 
proper ratio cannot be obtained 
by the use of the change-gears 
at hand, or when the gears of 
the desired numbers of teeth 
would be too small to connect 
properly, or too large to put in 
place, the method called com¬ 
pounding is used. Assume that 
the ratio of 4 to 1 is required. 
Referring to Fig. 98, a 36- 
toothed gear J is placed on the 
head shaft, and a 72-toothed 
gear L on the lead-screw. On the stud are placed two gears, a 48- 
and a 24-toothed, fixed to each other by placing them on a splined 
compounding sleeve which runs loosely on the stud. The 36-gear is 
engaged with the 48-, and the 24- with the 72-toothed gear, as 
shown. Front and edge views of these gears are given to show 
clearly their relative positions. 

The results of this combination are: If the 36-gear engaged the 
72-gear, the ratio would be 2; and if the 24-gear engaged the 48-gear, 
the ratio would also be 2. These ratios multiplied would be 4, as 
required. As shown, the ratios are: 36 to 48, ratio 1J; and 24 to 72, 
ratio 3—which ratios multiplied together produce 4. 

The effect, then, of introducing the 24- and 48-gears instead of 
a single intermediate (usually called an idle gear, as it does not affect 
ratios), is to double the ratio existing between the gear on the head 



74 










MACHINE SHOP WORK 


G3 


shaft and the gear on the lead-screw. The combination just 
described will cut a 16-pitch thread on a lathe having a 4-pitch 
lead-screw. (Usually a lathe will cut this thread without com¬ 
pounding. The gears shown and described are given merely as a 
simple example.) 

Should the above order of arranging the gears be reversed, the 
effect will be to divide the thread ratio instead of multiplying it; and 
instead of cutting 16 threads per inch, the lead-screw threads of 4 
to an inch will be divided by 4, producing 1, and the lathe will cut 
1 thread per inch. 

Lathes are usually provided with compounding gears of the 
ratios of 2 to 1—as 24 to 48, 36 to 72, and so on. But it is very 
convenient to have those of 3 to 1—as 24 to 72, 36 to 108, etc. 



Fig. 99. End and Front Elevation of Rapid Change-Gear Device 


It is always advisable to use as large change-gears as possible, 
as the revolutions of the lead-screw will be more regular and steady, 
the strain on the gear teeth will be less, and smoother and more 
accurate work will result. 

Rapid Change-Gear Devices. The more recent development 
of the thread-cutting mechanism of engine lathes aims to arrange 
the change-gears so that any desired thread may be cut without 
removing or replacing any of the gears. To accomplish this, all 
the necessary change-gears are permanently located in the lathe, 
and any one of them may be brought into use as required, by shifting 
one or more levers or equivalent devices. 

One of the most prominent of these devices is shown in Fig. 99, 
which illustrates, in A and B, respectively, an end and a front 
elevation of the device applied to an engine lathe. Motion is com- 


75 




























64 


MACHINE SHOP WORK 


municated from the main spindle by means of the. gear A on the 
head shaft, and through the gears B and C , to the supplemental 
shaft H, upon which is fitted a forked sliding arm G. This sliding 
arm G carries a pinion D splined to the shaft II, and also a con¬ 
necting pinion E journaled in it and capable of engaging either 
one of the sets of change-gears F, which are fixed upon the lead-screw 
J, by sliding the lever to the right or left, raising it until the gears 
engage properly, and permitting the pin on the thumb-lever K 
to enter one of the series of holes shown in the gear casing and thus 
secure the lever G and connecting pinion E in proper position to 
transmit motion for the supplementary shaft II to the lead-screw J. 

An index on the outside of 
the gear casing gives the 
necessary information as to 
the position of the lever G 
for any desired thread. No 
calculations are necessary. 

Size of Lathe. In this 
country, the size of a lathe 
is designated by the great¬ 
est diameter it will swing 
over the guides, and by the 
length of the bed. The 
lathe illustrated is known 
as a 14- by 8-inch. In 
England, the distance from 
the guides to the center is the unit of size, and, in a few 1 cases, 
the greatest distance between centers is considered to be the length 
of the lathe. Thus a 15-inch lathe in England would be a 30-inch 
lathe in the United States. 

Attachments. The attachments usually furnished without extra 
charge are a large faceplate of the full swing of the lathe, a steady 
rest, and a follower rest. The small faceplate is used only for driv¬ 
ing the work indirectly through suitable attachments. 

Faceplate. The large faceplate shown in Figs. 95 and 100 
is used as a direct support for the work, the T-slots and other open¬ 
ings being used for bolting and clamping the work firmly to the 
faceplate. 




Fig. 100. Heavy Faceplate 


76 

















MACHINE SHOP WORK 


65 


Steady Rest When work is being done on the end of a shaft 
so that the tailstock cannot be used, it is necessary to support the 
shaft in some other way. This is done by means of the steady rest, 
shown in Fig. 101. This consists of a frame hinged at A, and fitted 
with three movable jaws BBB. The rest is clamped to the lathe- 
bed in the proper place. The jaws BBB are then adjusted to form 


Fig. 101. 


Typical Center Rest 



a bearing for the work, care being taken that the axis of the work is 
parallel to the ways or shears. Unless it is parallel, the work will 
not be turned true; that is, the end will not be square, but will be 
hollowed or conical, as shown somewhat exaggerated in Fig. 102. 
The steady rest is also used to support or steady long shafts that are 
being turned. 


77 











66 


MACHINE SHOP WORK 


After adjusting the steady rest to size, it can be moved along 
the bed of the lathe without changing its relation to the lathe axis; 



Fig. 102. Diagrams Showing Effects When Work is Not Held True in Cutting 




but care must be taken not to reverse the steady rest in the lathe, 
as, in most cases, such action would necessitate a readjustment. 


78 



































































































































MACHINE SHOP WORK 


G7 


The names back rest and center rest are synonymous with steady 
rest, the use of the device often determining the name. 

Follower Rest. The follower rest serves some of the purposes 
of the steady rest, but is fastened to the carriage, and moves with 
it at the point of greatest stress. It may consist of adjustable jaws 
or a solid ring to slip over the piece being turned. It is especially 
valuable in turning shafting and other work where the ratio of.length 
to diameter is very great. 

Chucks. The lathe chuck, Fig. 103, consists of a body which 
is fastened to a special faceplate in such a way that it is concentric 
with the spindle. The three jaws AAA can be moved in and out 
toward or from the center, by turning the screw-heads B. These 
chucks are either uni¬ 
versal or independent. 

In the universal chuck, 
all the jaws are oper¬ 
ated simultaneously. 

That is, when one of 
the screw-heads B is 
turned, all of the jaws 
are moved an equal 
distance toward or away 
from the center. This 
makes it possible to put 
the work in position quickly if it is approximately round in its 
unfinished condition. With the independent chuck, Fig. 104, 
each jaw is operated separately. Such a chuck is used for holding 
pieces of irregular shape and those which must be held eccentrically. 
Frequently the universal and independent chucks are combined 
in one. Means are then provided for working the jaws separately 
or together as desired. 

In using the universal chuck, each screw should be tightened. 
The method of procedure is to place the work in the chuck, and turn 
one screw-head until all of the jaws are in contact with the piece to 
be worked on. Then turn the chuck, and tighten each screw-head 
successively until each one is tight enough. Owing to wear and 
lost motion, it is sometimes necessary to apply the wrench to each one 
three or four times before the final adjustment is effected. 



79 
















68 


MACHINE SHOP WORK 



Fig. 105. Faceplate Chuck Jaw 


Universal chucks generally have three jaws, while independent 
chucks have four. It follows that a combination chuck is not 
wholly satisfactory, because, with three independent jaws, it is 

very difficult to adjust work 
accurately, and with four 
universal jaws it is equally 
difficult to get every jaw to 
bear on the work. For cer¬ 
tain classes of work—espe¬ 
cially valves and pipe fit¬ 
tings—chucks with two jaws 
are often used. 

The large faceplate of a 
lathe can be made into an 
independent chuck by attach¬ 
ing what are known as faceplate jaws. Fig. 105. In this case, 
there may be six, eight, or more jaws. 

As work chucks are expensive, it sometimes happens that a 
piece is to be held for which no provision is made. A chuck can then 
be made of wood, as shown in Fig. 106. Two pieces of wood A and 
B are bolted together by the bolts EE, while separated by the 

filling pieces CC. The piece is 
firmly bolted to the faceplate 
by the bolts DD . The lathe is 
then run at high speed, and the 
interior bored out exactly the 
size of the piece that is to be 
held. The nuts of the bolts 
EE are slackened, and the 
filling pieces CC removed. The 
piece to be worked on is then 
inserted, and by tightening the 
nuts EE, it is securely clamped 
between the pieces A and B. 
Lathe Dogs. As the fric¬ 
tional contact of the work on the live center is not sufficient to 
turn it, some device must be used to make the work turn with the 
center. To accomplish this, a lathe dog is used. For round work. 



Fig. 106. Emergency Chuck 


80 






















MACHINE SHOP WORK 


69 



Fig. 107. Lathe Dog for 
Round Work 


such as shafting, a dog like that shown in Fig. 107 is often used. 
The shaft or piece to be turned is placed in the hole A, and held 
firmly in place by the setscrew B. The tail-piece C is put through 
a hole in the faceplate, and the work rotates 
with the live center. 

While this type of dog is satisfactory in 
most cases, the contact between the dog and 
the faceplate being beyond the end of the 
piece, introduces a bending strain which is 
appreciable in slender work. To avoid this, 
dogs are made with a straight tail, and driven 
by a stud projecting from the faceplate. 

For work other than round, a dog such as 
that shown in Fig. 108 may be used. The 
piece to be worked on is placed between the 
jaws, and held in position by the bolts. 

The holes in the upper jaw are made larger 
than the screws, in order that the angle 
between the jaws may be varied. The con¬ 
nection between the faceplate and dog is made as with Fig. 107. 

Mandrels. Another method of holding work is by the use of a 
mandrel. This is a piece of steel with a slight taper; the ends are 
flattened for the i lathe dog, as 
shown in Fig. 109. It frequently 
happens that a piece with a hole 
in it is to be turned or finished 
over its outer surface. In this 
case a dog cannot be used, and 
it is troublesome to hold it in a 
chuck. Such a piece is shown 
in Fig. 110. This is a stuffing- 
box gland. If it were to be 
held by the jaws of a chuck, 
the face could not be reached 

at all, and only a portion of the edge B, whereas a dog clamped 
to it would offer even greater obstruction. The method of using 
the mandrel is to ream the gland out, so that it can be driven 
upon the mandrel. When this is done, the frictional resistance 



Fig. 108. Clamp Dog 


81 










70 


MACHINE SHOP WORK 


between the two will be sufficient to drive the piece. So held in 
place, it can be finished over its outer surface with but one setting 



Fig. 109. Work Mandrel 



Fig. 110. Stuffing-Box Gland Held on Mandrel 


in the lathe. All finishing possible may be done while it is in 
the chuck, leaving, in this case, only the face A and edge B to be 

finished while on the 
mandrel. 

Should the gland be 
shaped, as shown in Fig. 
Ill, it would be neces¬ 
sary to make a special 
mandrel to fit the bore. 
The cylindrical part A 
of the mandrel must be 
a driving fit, and the 
part B a loose fit. 

Expanding Man¬ 
drels. Where a mandrel 
like that shown in Fig. 
109 is frequently used, 

Fig. 111. Sttiffing-Box Gland Requiring Special Mandrel ,i , , ■. . . * 

the constant driving of 
the work on and off will wear the mandrel to a smaller diameter, 
causing it to become useless. Again, solid mandrels are usually 




82 










































MACHINE SHOP WORK 


71 


made of standard diameters, varying by sixteenths of an inch. It 
sometimes happens that a piece to be turned has a hole which will 
not fit any standard solid mandrel. 

To overcome these difficulties, an expanding mandrel shown 
in Fig. 112 is much used. This is really a chuck, so arranged that 



Fig. 112. Diagram Showing Use of Expanding Mandrel 


the grips can be forced out against the interior of the hole. When 
the work has been finished, the grips are again drawn in and the piece 
removed. Another form of expanding mandrel is shown in Fig. 113. 



Fig. 113. Another Form of Expanding Mandrel 


Cutting Tools. General Characteristics. The cutting tools used 
in lathes are of a great variety of shapes. These shapes are adapted 
to the work that is to be done, and to the kind of finish that is to 
be left upon the metal. There are two fundamental requirements 
that all tools must fulfil: 
the cutting edge alone must 
touch the metal; the edge 
must be keen. A typical 
form of tool is shown in 
Fig. 114. The cutting edge 
of the tool at A is in con¬ 
tact with the work. The 
bottom line AB runs back 
from the metal and does not touch it. The top face AC slopes down 
and back. The line AD is a tangent at the cutting point, and the 
line AE is radial at the same point. Therefore, the angle DAE 



83 
















72 


MACHINE SHOP WORK 


is always a right angle. The angle DAB is called the angle of 
clearance, and should be small—in lathe tools, not over 10 degrees. 
The angle CAE is called the angle of rake, and should be as 
great as circumstances will permit—about 20 degrees on lathe tools 
for wrought iron and steel, leaving 60 degrees for the solid or 
cutting angle, which is the same angle as that used in the case of 
the ordinary cold chisel. 

Material. The physical qualities of the material to be turned 
will to a great extent determine the cutting angles of the tool—first, 
as to whether it is hard or soft; and second, whether it is crystalline 
or fibrous. The degree of hardness of a material determines how 
much can be removed in a given time, or—which amounts to the 
same thing—whether the speed of the cutting shall be fast or slow, 
and whether the feed shall be coarse or fine. A crystalline or fibrous 
nature will make considerable difference in the top angles of the tools, 
and this will be readily seen in the tendency of a crystalline metal 
(as cast iron) to break up into small chips, while the fibrous turnings 
(as wrought iron) will curl off into spiral or helical shavings. There¬ 
fore the fibrous material will require tools of sharper angles than 
those for a crystalline metal. 

For cutting soft brass and other similar metals, the top surface 
AC of the tool will be practically level, while the face angle BAD 
will be 3 degrees or frequently less. 

Clearance. Clearance prevents the tool from rubbing on the 
work, while rake adds to the keenness of the cutting edge, and gives 
freedom to the removal of the chips. A tool should have sufficient 
strength at the point to do the work required. 

Betting the Tool. The tool should be set so that the cutting edge 
will coincide very nearly with a horizontal line passing through 
the axis of the work. Most machinists set the cutting edge a little 
above this horizontal line. When so set, the stress tends to force 
the tool down along the line of its greatest strength. The tool 
may, however, be set too high. If this is done, as in Fig. 115, the 
angle of clearance will disappear, and the curve of the work will 
rub against the bottom of the tool. This will tend to force the tool 
out; it will heat the steel and produce a rough surface on the metal 
being turned. If, on the other hand, the tool is set too low, as in 
Fig. 116, the cutting edge does not stand in line with the motion 


84 


MACHINE SHOP WORK' 


73 


of the work at the point of contact. The result will be that the 
metal will be scraped rather than cut, as there is no rake; and the 
pressure upon the tool will be in the line of its least resistance, as 
indicated by the arrow. Such a position might cause the point 
of the tool to break off. It will also cause the tool to tremble or 




chatter as it removes the chips, leaving a rough and wavy surface 
on the metal. 

As stated above, most machinists prefer to set the cutting edge 
a little above the center. The amount the tool is set above the 
center is slight, and of course depends upon the character of the 
work, and upon the shape of the cutting tool. The angle ACB, 
Fig. 117, should be only about 5 or 6 degrees. 

Tool=Posts. The tool is usually held to the carriage by means 
of a tool-post, shown in Fig. 118. The post consists of a piece 
with a slotted hole through the center for the tool B. A ring C 
slips over the post and rests upon the body of the carriage. This 
ring may be beveled as shown, to provide vertical adjustment for 
the point of the tool. The 
post has a collar D at its 
lower end, that goes loosely 
into a slot in the carriage. 

At the top there is a set 
screw E. When the tool 

has been properly adjusted Fig. 117. Standard Setting with Cutting Edge of 
. . , . Tool a Little Above Center 

by turning the ring C to give 

it the correct elevation, the set screw is tightened down upon the top 
of the tool. This raises the tool-post to a bearing on the under side 
of the slot, and clamps the whole firmly in position. 

In setting the tool, it should be done with the cutting 
edge as far back toward the supporting ring as possible. If it 



85 
















74 


MACHINE SHOP WORK 


has too much overhang, as shown by the dotted lines of 
Fig. 118, it will spring under the pressure of the work and will 
tend to chatter. 

While this form of tool-post is used more than any other, there 
are certain objections to it. In the first place, changing the height 



of the tool-point also changes the angles of rake and clearance. 
These are supposed to be correct when the base of the tool is hori¬ 
zontal. Any change from this position will alter these angles 
materially. Again, this post is not rigid enough for heavy work. 
On lathes of over 30-inch swing, the style of tool-holder shown in 

Fig. 119 is often employed. 
English manufacturers use it 
almost exclusively on all 
sizes. There is no provision 
for raising and lowering the 
point of the tool; and while 
this is not of serious impor¬ 
tance on large lathes (30-inch 
and over), it becomes a mat¬ 
ter of moment when turning 
the kind of work which as is usually handled in lathes of 14-inch 
and 16-inch swing. 

The type of tool-post shown in Fig. 120 has two beveled rings 
to adjust the height of the tool. 
































MACHINE SHOP WORK 


75 


The Lipe tool-post shown in Fig. 121, combines the good points 
of all the other types; the tool can be held by one or two screws 
as the character of the work may require, and the tool may be 
adjusted vertically and hor¬ 
izontally after being clamped 
down. The construction and 
operation of this tool-post 
are so evident from the illus¬ 
tration, that further descrip¬ 
tion will not be given. 

An entirely different 
method of adjusting the tool 
point is by means of what is 
called the elevating or rise- 
and-fall rest, shown in Fig. 

122. In this type, there is 
a T-shaped casting carried on 
the upper part of the carriage, 
supported by trunnion screws 

at the front, and by an adjust- Fig. 120. Bevel Ring Tool-Post 




87 




































76 


MACHINE SHOP WORK 


ing screw at the rear. With this is used a tool-post as shown in 
Fig. 118, with a plain ring. The elevating rest is used quite 
extensively on small lathes, but the convenience of adjustment 
is gained by a loss in rigidity. The cross-rail is slender; and the 



Fig. 122. Tool-Post with Rise-and-Fall Rest 


elevating portion, being supported at three widely separated 
points, lacks stiffness. As the effective swing over the carriage 
is limited by the height of the cross-rail and by the parts 
carried above it, they are made slender—in fact, too slender in 
many cases. 

Turning Tools. Side or Facing Tool. A very common form 
of lathe tool is shown in Fig. 123. It is used for squaring up the 
ends of shafts, facing shoulders, and similar work. While the 
ordinary forms will not remove a large amount of metal, they can, 
when made thick and heavy, be used for making roughing cuts 
on the surface of cylindrical work. The common form is made 



Fig. 123. Side or Facing Tool Fig. 124. Diamond Point 

slender in order to work between the dead center and the piece in 
squaring up ends. 

Diamond Point. A common form of tool for turning wrought 


88 


























MACHINE SHOP WORK 


77 


iron and steel is the diamond point, shown in Fig. 124. The name 
is derived from the shape of the top face. This tool has both front 
and side rake, which form a keen edge without reducing the strength. 
It is used for finishing only when the point is ground slightly round¬ 
ing and a fine feed is used. In finishing, but little metal should be 
removed. 

The feed of a tool is the amount of longitudinal advance at 
each revolution of the work. 

For roughing out cast iron, a strong and rapid working tool 
is a round nose with considerable side rake. For finishing wrought 



Fig. 125. Tool for Finishing Wrought Fig. 126. Tool for Finishing Cast Iron 

Iron and Steel 


iron and steel, a modification of the diamond point, as shown in 
Fig. 125, is often used. For cast iron, a square-nosed tool, Fig. 126, 
should be used. The square-nosed tool must be carefully ground 
and accurately set; otherwise it is very likely to gouge into the 
softer parts of the metal. When finishing wrought iron and 
steel, the tool should be liberally supplied with oil or soda water. 
Cast iron must always be worked dry, both in roughing and 
finishing. 

Cutting-Off or Parting Tool. This tool is illustrated in Fig. 127. 
The blade is quite narrow—as narrow, in fact, as the character of 
the work will allow. As the blade needs to be narrower at the shank 
and at the bottom than it is at the cutting edge, it follows that the 
tool will be weak. It must be set 
horizontally, so that, as the tool is 
fed to the work, only the cutting 
edge will touch the metal. It must 
also be set SO that the cutting edge Fig. 127. Cutting-Off or Parting Tool 
will pass through the axis of the 

work as it is fed to the center. If set too high, it will cease to 
cut before the center of the work is reached; while if too low, 
the tool has a poor scraping action, and will leave a portion of the 
work uncut. On work held between centers, one should not attempt 



89 




















78 MACHINE SHOP WORK 

to cut to the center of the piece, as the work will surely ride up 
onto the tool. 

Boring Tools. The term boring as used in machine practice 
usually means methods of machining internal surfaces, other than 
- those of common drilling and 

. J nn n r^ — T7 reaming. Also methods for 

"HEP 7 ! r IP' holding the work other than 

Fig. .28. General Form of Boring Tool those Common to Ordinary drill- 

ing and chucking operations 
are often used. When boring machine parts, use may be made 
of the common inside turning tools or of special appliances termed 
boring bars. 

When a hole is to be bored in lathe work, tools of a shape different 
from those used in turning should be used. The general form of the 
tool is shown in Fig. 128. The length 
of the shank depends on the depth of 
the hole to be bored, for it must be 
long enough to reach from the tool-post 
to the bottom of the hole. This over¬ 
hang makes the tool more likely to 
spring, and necessitates a much lighter 
cut being taken than when removing 
the same amount of metal by outside 
turning tools. The result of this lighter 
cut is seen in the increase of time 
required to remove a given amount of stock. The shape of the 
cutting edge is practically the same as that of the tools for turn¬ 
ing, except that the boring tool must have more clearance to 
avoid striking the work. Therefore, with the same solid angle, 

--the tool will have less rake. The 

||||r""liiilllj | , "! | !!|,' l ""i||'' !ll l||||| reason for this will be seen by com- 

paring Figs. 114 and 129. In Fig. 

Fig. 130. Tool for Boring in Brass 114> it wiU be seen that the surface 

of the work is outside a tangent at the cutting point and can never 
interfere with the bottom of the tool. In Fig. 129, the surface of 
.the work is inside the tangent, and, unless the tool has a large 
amount of clearance, it will cause trouble by striking the concave 
surface. 



Fig. 129. Boring Tool Set for 
Clearance 


90 











MACHINE SHOP WORK 


79 


Tools for brass differ from those used on steel and iron in that 
they have no rake. A tool suited for working brass is shown in 
Fig. 130. Brass does not readily split, and the chips break off as 
soon as started from the main body. When turning wrought iron 
and steel, on the other hand, the metal does not break, but forms 
long spiral chips if the tool is in good condition. If a tool with rake 
is used in turning brass, the work will not only be rough in appear¬ 




ing. 131 . Common Forms of Slide-Rest Tools. A —Left-Hand Side; B —Right-Hand Side; 
C —Right-Hand Bent; D— Right-Hand Diamond Point; E —Left-Hand Diamond Point; 

F —Round Nose; G —Cutting-Off; H —Roughing; I —Threading; J —Bent Thread¬ 
ing; K —Boring; L —Inside Threading 


ance, but there is great danger of the tool gouging into the stock 
and spoiling the work or tool, possibly both. The finishing tools 
for brass may be square or round-nosed, without rake; in fact, a 
small amount of negative rake will produce a much better surface. 
When the brass contains a large percentage of copper, some rake 
to the tool may be required, owing to the ductility and toughness 
of the metal. 

Fig. 131 shows common forms of lathe tools. 


91 


80 


MACHINE SHOP WORK 


The shape of the tool has a very important influence on the 
amount of work it can be made to do. As has already been explained, 
these shapes vary with the different metals that are being worked, 
and also with the class of work performed. It is highly important 
that the cutting angles be correctly formed. While hand-grinding 
on the emery wheel and grindstone is fairly satisfactory, the best 
results can be obtained only by the use of a regular tool-grinding 



machine, such as that shown in Fig. 132. In addition to the grind¬ 
ing, tools for fine finishing should be carefully whetted on a fine 
oil-stone. 

Cutting Speed. Importance of Speed Element The speed at 
which cutting is done is an important matter. This varies with the 
shape of the tool, the quality of the metal being worked, and the 
strength of the lathe. The amount of metal removed in a given 


92 





































MACHINE SHOP WORK 


81 


time is, therefore, equally variable. It is impossible to make a 
correct estimate of the time that a given piece of work will require, 
unless all of the above elements are known. For approximate 
estimates, the cutting speed for carbon tool steel cutting tools may 
be taken to range about as follows: 


In cast iron.from 30 to 40 feet per minute 

In wrought iron.from 25 to 30 feet per minute 

In steel.from 15 to 40 feet per minute 

In brass.from 60 to 100 feet per minute 


Suppose a wrought-iron shaft 6 feet long and 4 inches in diam¬ 
eter is to be turned. Let the lathe be capable of carrying a feed 
of -£5 inch per revolution. The shaft has a circumference of 
4X3.1416 = 12.5664 inches. To give the tool a cutting speed of 25 

25x12 

feet per minute the shaft must make = 24 revolutions per 

minute (approximately), giving a feed of y^X24 = f inch in that 
interval of time. With a travel of § inch per minute, it will take the 
cutting tool on the lathe carriage (6Xl2)^f = 96 minutes to take 
a cut the whole length of the shaft. 

The amount of feed is really the governing element. This may 
be as much as inch per revolution, and, for finishing cuts, may 
not be more than inch. The depth of the tool cut also influences 
the time required to finish a given piece of work, and this may vary 
from to \ inch, depending entirely upon the shape of the tool 
and the strength of the lathe. 

Speeds for High-Speed Steel. The cutting speeds given above 
are what may be used with the best grades of tool steel, such as 
Jessop’s; but by using air-hardening or tungsten steels, the speed 
of cutting may be very much increased over the values given above. 
These high-speed steels are rapidly coming into favor, more especially 
for heavy roughing cuts. 

With the aid of these steels, the cutting speeds have been in¬ 
creased, and the chip is made heavier in both depth and feed, up to 
the point where the lathe refuses to carry the load. The ability of 
this quality of steel to stand without injury, the high temperatures 
resulting from the fast feeding, is the feature which enables it to 
perform the work at this rate. 


93 







82 MACHINE SHOP WORK 

For what are now known as the high-speed steel tools, the speeds 
for the different metals mentioned will be as follows: 

Soft cast iron. 50 to 60 feet 

Hard cast iron. 20 to 40 feet 

Hard cast steel. 30 to 40 feet 

Soft machine steel. 60 to 90 feet 

Hard machine steel. 20 to 30 feet 

Wrought iron .. 35 to 45 feet 

Tool steel, annealed. 50 to 80 feet 

Tool steel, not annealed. 15 to 20 feet 

Soft brass.'.110 to 130 feet 

Hard brass.*. 90 to 110 feet 

Bronze.. . 60 to 80 feet 

Bronze, “gun metal”. 40 to 60 feet 

Gray or red fiber. 40 to 60 feet 


Usually an increase in speed must be accompanied by a reduc¬ 
tion in the feed—that is, in the number of revolutions of the work 
per inch of movement of the tool. The following directions will be 
proper in this respect: 

Roughing cuts on soft cast iron may be made with a feed as coarse as 4 to 
5 per inch, with a strong round-nosed tool. 

Roughing cuts on soft machine steel forgings, 5 to 8 per inch. 

Sizing cuts on soft cast iron, 12 to 16 per inch. 

Sizing cuts on soft machine steel, 16 to 20 per inch. 

Finishing cuts on soft cast iron, with a narrow-point tool, 15 to 25 per 

inch. 

Finishing cuts on soft machine steel, with a narrow-point' tool, 20 to 40 
per inch. 

Finishing cuts on soft cast iron, with a wide point, practically a straight- 
faced tool with the corners slightly rounded, 1 to 4 per inch. 

Under the same circumstances, for a soft machine steel, 4 to 8 per inch. 

Brass will be turned with feeds of from 10 to 40 per inch, according to the 
kind of cut and shape of the tool. 

Fiber will stand a heavy feed in proportion to the speed. 

Cooling the Tools. For cooling the tool while performing heavy 
duty, a solution of sal soda is preferable to water, as it prevents 
rusting of the work and machinery. Its office is simply to keep the 
tool cool. If a tool becomes overheated, the edge begins to turn 
over and it becomes dull. 

Referring to Fig. 116, it will be seen that the chip, as it is being 
removed, presses down on the top face of the tool. This pressure 
increases with the depth of cut and the feed. The resulting friction 
would soon cause a high temperature in the tool if it were not 


94 















MACHINE SHOP WORK 


83 


reduced by the lubricant. The lubricant cools the tool by absorb¬ 
ing a portion of the heat, and lessens the amount of heat developed 
by reducing the friction between the tool and the chip. Clean, 
pure water is the only lubricant which can be used on cast iron; 
but the rapid rusting which follows its use makes it undesirable, 
and as a result cast iron is usually turned dry. Brass is also usually 
turned dry. Prime quality lard oil is sometimes used for cooling 
the tool; but the greater cost prevents its extended use, unless 
some means are provided for collecting, separating, and filtering it. 


LATHE OPERATIONS 

Mounting Work on Lathe. Centering Method'. A piece to be 
turned is supported on the two centers of the lathe. In order 
that this may be done, it is prepared by drilling and countersinking 



Fig. 133. Hole and Center of Correct 
Angle for Centering Work 



Fig. 134. Effect of Using Different 
Angled Hole and Center 


a hole in each end. This is called centering the work. The counter¬ 
sink should be of exactly the same angle as the lathe center upon 
which it is to run. The hole should be drilled deep enough so that 
the point of the lathe center may not strike. The shape of the hole 
is shown in Fig. 133. The generally accepted standard angle is 60 
degrees. The effect of using a 60-degree hole on a 90-degree center 
is shown in Fig. 134. The result of such an application is that the 
bearing will be concentrated on a line AB, causing rapid wear of the 
outer end of the hole, and a cutting of the dead center. 

The size of center holes varies with the weight of the work and 
the character of the operation. Heavy work and rough turning 
require large center holes, while small work and fine turning can be 
done without countersinking deeply. As bearing surfaces in cast 
iron must be large to be satisfactory, center holes in cast iron are 


95 





























84 


MACHINE SHOP WORK 


likely to give trouble by unequal and rapid wear. When turned 
work in cast iron must be very accurate, it is well to drill a large 
hole in each end, drive in a plug of wrought iron or mild steel, and 
form the center holes in the plugs thus driven. 

When the piece to be turned has been put in place, the dead 
center should be oiled and screwed up into position. It should 
be tightened so that there is no lost motion, and yet allow the work 
to turn freely. 

Chuck Method . The turning of shafts.and bars is not, however, 
the only kind of work to be done on a lathe. Pieces are to be turned 



that are thin, that have holes through the center, and which are 
so shaped that they cannot be held upon the centers. In such cases 
it becomes necessary to hold the work firmly without distortion. 
This may be done by use of the lathe chuck. 

Faceplate Method . Still another method of holding a piece 
to be worked is that shown in Fig. 135. The piece is clamped 
to the faceplate. When this is done, there should be a bearing 
on the faceplate immediately beneath the clamping strap. For 
example, consider Fig. 136. Suppose a disc having four feet on one 
side is to be faced off on the front. The clamps should be placed 
directly over the feet, as in B. If they are placed between the feet 


96 


























MACHINE SHOP WORK 


85 


at EE, the work will be sprung out of shape, as shown by the dotted 
lines in A . Then, when the tool has done its work, the shape of 
the piece, while bolted to the faceplate, will be as shown in C . As 
soon as the pressure of the straps is removed, the elasticity of the 



metal will cause the piece to assume the convex form shown in D; 
whereas, if the straps had been placed as shown in B, no distortion 
would have been produced. 

An angle iron may be clamped on a faceplate, as shown in 
Fig. 114, presenting a surface parallel to the lathe axis, to which 




Fig. 137. Angle Iron Clamped to Faceplate and Counterbalanced 


work may be attached. The angle irons may, of course, be at any 
angle to the faceplate, but 90 degrees is the one most commonly 
used. When work is held in this manner, it is desirable to counter¬ 
balance it, as is also shown in Fig. 137. 


97 




































86 


MACHINE SHOP WORK 


Adjusting Pieces to Center on Faceplate. Whenever a piece 
is to be turned on a lathe faceplate, it is necessary to adjust it so 
that its rough outline is approximately concentric with the lathe 
centers. This is done by bolting it lightly to the faceplate and run¬ 
ning the lathe. While running, a piece 
of chalk is held so that the projecting 
portions will strike it. This marks the 
piece, and indicates the part that is 
farthest from the center. The lathe is 
then stopped, and the piece shifted, 
moving the chalk mark toward the lathe 
axis. This is repeated until the chalk 
makes a continuous mark around the 
whole circumference. The piece may 
then be considered to be centered. 

Suppose it is necessary to center a 
piece having a hole that must run true. In this case the inside of 
the hole must be used as a guide. Let Fig. 138 represent the hole 
with the thin shell, and A a chalk mark made as described for cen¬ 
tering by the outside. In this work the chalk mark must be 
removed away from the axis. A lathe tool may be used, as 
shown in Fig. 139, to center a piece that is to be bored. 

Where a piece has 
already been turned, 
greater accuracy is de¬ 
manded, and a surface 
gage may be used to ad¬ 
vantage. Set the gage on 
the bed or carriage of the 

Fig. 139.- Use of Lathe Toolm Centering Piece l at he, and place One of the 

points in contact with the 
vork. Rotate the work as before, and note where the point touches 
the surface. This point is to be treated in the same way as the 
chalk mark explained in a preceding paragraph. 

A still more accurate method of centering a piece of turned work 
on a faceplate, is to use some form of graduated indicator, such 
as the Starrett indicator, shown in Fig. 140. This is held in the tool- 
post, the contact-point brought against the work until the indicating 




98 


















MACHINE SHOP WORK 


87 


arm is at zero. If the work is now slowly rotated by hand, the 
indicator will show just where the work is out of true, and being 
graduated in thousandths of an inch, will also show how much. 



By careful adjustment, the piece may be centered to the degree of 
accuracy required. 

Instead of locating a cylindrical surface concentric with the axis 
of the lathe, it often happens that a point is to be located in the 



axis. For this purpose, the center indicator, Fig. 141, is used. 
The free end of the short arm is placed in the point to be centered 
(usually a prickpunch mark), the fulcrum being held in the tool- 


99 


























88 


MACHINE SHOP WORK 


post. When the work is rotated, the free end of the long arm 
not only shows the error, but magnifies it in proportion of the length 
of the short arm to the length of the long arm. By using a com¬ 
paratively long arm, the point can be very closely centered. 

Centering Finished Work. After making the center punch 
mark in the end of the piece, it is drilled and countersunk. This 
must be done very accurately, but frequently the drilled hole or 
the countersink will not be in the exact center, Fig. 142. This 
may be caused by uneven grinding of the drill, eccentric motion of 
the drill point (due to the inaccurate running of the spindle), or 
the distortion of the metal by the center punch. If the countersink 
is not exactly in the center, it must be drawn back to the center. 



Hole 



This is generally done with a small round-nosed chisel and a hammer. 
The method of doing this is as follows: After making the center 
punch mark, the hole is drilled and then countersunk slightly. The 
work should now be stopped; and if the circumference of the conical 
hole is not concentric with the circumference of the piece, a groove 
should be cut down the side farthest from the outer circumference, 
as shown in Fig. 143. The depth of the groove, which should be 
near the center, depends upon the amount of eccentricity. The 
countersink is again started, and the groove drilled out. If the circle 
is not yet concentric, the process is repeated. 

Turning. Facing or Squaring Up. The first operation usually 
performed on a piece of work when placed in the lathe is facing 
or squaring up the ends. This must be done to get a uniform bearing 
for the centers. The finishing of all surfaces at or nearly at right 
angles to the axis of the work, is classed as facing, and the side tool, 


100 













MACHINE SHOP WORK 


89 


Fig. 123, is usually employed. For roughing cuts, the cutting 
face of the tool is placed at a slight angle to the work surface, in 
order to remove the metal quickly; but for finishing cuts it is placed 
nearly flat against the work, so that a light, thin chip may be taken. 

Turning a Cylinder . Turning the cylindrical portions of the 
work is next done by the use of the diamond point or similar tool. 
Roughing cuts are taken to within about inch of the finished 
size, and a fine finishing cut reduces the work to the exact diameter. 
For roughing cuts common calipers should be employed; while 
for finishing cuts, the micrometer caliper is most suitable. All 
measurements must be taken with the lathe at rest, as motion of 
the work renders close calipering impossible. 



Turning a Taper. It frequently happens that a piece must be 
turned tapering; that is, one end is to have a greater diameter than 
the other. There are three ways of accomplishing this result: (a) 
setting over the dead center, (b) the use of the compound rest, 
and (c) the use of the taper attachment. 

Setting over Dead Center . Setting the dead center over is the 
more common method. Provision is generally made for moving 
the dead center laterally toward the front or rear of the bed accord¬ 
ing to the taper required. With the dead center set over, the 
tool will be at unequal distances from the live and dead centers, 
because its movement is parallel to the axis of the lathe. This 
is shown in Fig. 144. The piece to be turned is placed upon the 
centers A and B , and the dead center is moved from the axis a 
distance equal to the difference between the radii AD and BC. 


101 








90 


MACHINE SHOP WORK 


This leaves the side DC parallel to the center line of the lathe; hence 
the tool will be fed along this line. The objection to doing work 
by this method is that the lathe centers do not have full bearings 
at the ends of the work, and the center holes are likely to wear out 
of their true positions. 

If the taper is to be turned on a piece held by a mandrel, or if 
the taper is to extend but a part of the total length of the w T ork, the 
amount of set-over for the dead center must be calculated in the 
same manner as though the taper were to extend the whole length of 
the mandrel or work. In other words, the amount of set-over for 
the dead center is determined by the distance between the centers 
B and the rate of taper. 

For example: Suppose 
the mandrel in Fig. 145 to 
be 16 inches long; and the 
piece of work CD, which 
is to be turned tapering, 
is 4 inches long; suppose 
also that the diameter at 
D is to be | inch smaller 
than at C. Then, for one inch of length, the difference in diam¬ 
eters would be one-fourth of | inch, or ^ inch; and for a length 
of 16 inches, it would be sixteen times ^ inch, or 1 inch. Since the 
set-over is equal to the difference of the radii, the set-over for the 16 
inches would be one-half of 1 inch, or ± inch. This, then, would be 
the set-over for the work under consideration, and for any piece to 
be tapered at the rate of J inch in 4 inches when held on a 16-inch 
mandrel. In accurate work, the distance to which the centers 
enter the mandrel must be considered. 



Fig. 145. Turning Taper on Piece Held by'Mandrel 


The machinist generally sets over the dead center as accurately 
as possible and takes a roughing cut. The taper is then tested by 
a careful comparison of the diameters, or by trying it in a tapered 
hole of the proper angle, and setting the center more accurately. 
Setting over the dead center does not give accurate results, on 
account of the fact that the centers do not have a true bearing at 
the ends of the work. Naturally, the shorter the work, compared 
with the amount of set-over, the greater the inaccuracy because of 
the greater nearness of the centers. 


102 




















91 


MACHINE SHOP WORK 

EXAMPLES FOR PRACTICE 

1. A tapered bushing 3 inches long and of 4 and 4^ inches 
outside diameters, is driven on a 12-inch mandrel for turning. How 
much must the dead center be set out of line in order to do the work? 

Ans. 1 inch 

2. A connecting rod 6 feet long is to be turned tapering from 
the center to the neck back of the stub ends. This distance is 26 
inches. The diameter at the center is to be 3 inches, and at the neck 
2 \ inches. How much offset must be given to the dead center? 

Ans. .692-J- inch 

3. A shaft had a taper 2 feet long turned on one end. The 
large end of the taper was 4 inches in diameter, and the small end was 



Fig. 146. Compound Tool Slide 



3 inches in diameter. The dead center was set over 1 inch. How 
long was the shaft? Ans. 4 feet 

Compound Rest. In turning a taper with the compound rest, 
the work may be held in a chuck, on the faceplate, or between 
the centers. The compound rest, Fig. 146, is then set at such an 
angle that the direction of motion of the tool will coincide with the 
required taper. Several methods are employed for this adjustment 
of the rest. The tool is fed to the work by means of the feed-handle 
A attached to the compound rest. 

Taper Attachment. The taper attachment, Fig. 147, is in the 
form of a guide which is bolted to the back of the lathe. It can be 
set at any desired angle with the axis of the lathe, the limit usually 


103 























92 


MACHINE SHOP WORK 


being a taper of about three inches per foot. The guide is graduated 
so that calculations based on the length of the work are unnecessary. 
A slide moving with the guide is attached to the cross-feed slide 
of the carriage. This cross-feed slide is loosened, and, while the 
carriage is moved by the feeding mechanism, the tool is moved 
in or out according to the direction of the taper. 

One of the important points to be observed in turning tapers, 
is to have the cutting point of the tool exactly level with the centers. 
If this is not done, the work will not be truly conical, and the rate 
of taper will vary with each succeeding cut. 

In case an internal and an external taper are to be turned so 
as to form a fit, the internal taper should, if the character of the 



Fig. 147. Taper Attachment 


work will permit, be made first. After this has been done, the ex¬ 
ternal taper should be turned and tested several times during the 
process. The external taper is first turned as accurately by meas¬ 
urement as possible, taking care that the piece is made a trifle large. 
Draw a chalk line on the external taper, from one end to the other; 
press the tapers together, and give one of them a slight twist. On 
separating the tapers, the rubbing of the chalk will show where 
the work was in contact, and, by resetting the lathe and repeating 
the process, a very accurate fit can be obtained. 

Turning Shafting. Shafting is usually turned * inch less 
than the nominal diameter. For instance, instead of a shaft 2 
inches in diameter, one of 1 inches in diameter is used. The 
reason is that iron of a nominal diameter of 2 inches, usually ^ 


104 




MACHINE SHOP WORK 


93 


inch over size can be used. Before turning a length of shafting, 
the rough bar should be carefully straightened. After the center 
holes have been drilled and the piece placed in the lathe, the work 
can be rotated, and the eccentric portions marked with chalk. 
When this has been done, the bar should be removed from the 
lathe and sprung back into true alignment. It is well to take two 
cuts in finishing shafting, one for the roughing cut, and one very 
fine finishing cut. The tool for the latter part of the work should 
be kept flooded with oil or with a solution of sal soda. If the work 
is light, a tool holder, carrying both the roughing and the finishing 
tools, should be used. This makes it possible to do the work in 
practically the same time as for one cut. 

Preventing Spring in Shafting. As a length of shafting is likely 
to spring under the pressure of the tool, some method of preventing 
such action must be employed. A steady rest can be used. It 
is, however, inconvenient, and must be frequently moved, or at times 
it will stand too far from the tools. Furthermore, as the rough 
bar will neither be truly round nor concentric with the centers, 
it is necessary to turn spots for the center rest. This operation 
takes considerable time, owing to the fact that very light cuts must 
be taken in order to avoid springing the bar. The best method 
is to have a ring attached to the tool holder; the internal diameter 
of this ring is that of the finished shaft. It is slipped over the tail- 
stock center, and follows the finishing tool. It must, of course, 
be rigidly fastened to the tool holder. In this way the shaft is sup¬ 
ported close to the tools; the ring also serves as a gage to measure 
the diameter of the shaft. If, for any reason, the tools turn to a 
larger diameter than the inside of the ring, notice is immediately 
served upon the workmen to that effect, by binding in the ring. 

Eccentric Turning. The term “eccentric” is given to a rotating 
machine part which is used to “throw” a mechanism eccentric 
with its main center line. Eccentrics may be said to include all 
crank motions, also many cam motions. In general shop terms, 
however, an eccentric is a machine part having an outer circle 
which is off center or eccentric with its shaft. 

In construction it may be machined as a part of its own shaft, 
as in Fig. 148, or it may be so made as to slip onto a shaft in which 
case provision must be made for keying it to the shaft. 


105 


94 


MACHINE SHOP WORK 


Throw of Eccentric. The throw of an eccentric may be taken 
as the radius of eccentricity or it may be made to mean twice the 
radial eccentricity. 

Machining Eccentrics. While eccentrics may be machined in 
a variety of ways, the accompanying text will consider the lathe 




only. If the eccentric is of the simple form of two circles with 
their centers offset in relation to each other, the work must be done 
on a mandrel provided with two sets of centers, one pair for each 
circle, Fig. 149. 

Eccentric Solid with Shaft. In this case if the throw of the 
eccentric is less than the radius of the shaft, both sets of work cen¬ 
ters may be made in the shaft ends, as in 
Fig. 150. Where the throw is too great to 
allow this, some provision must be made 
for the second set of centers. 

Two methods for doing this are in com¬ 
mon use, (a) casting or forging lugs upon 
each end of the shaft sufficiently large to in¬ 
clude the needed centers, (b) use of attach¬ 
ments for the shaft ends,the attachments them¬ 
selves being provided with the desired centers. 

Eccentrics Not Solid with Shaft. Eccentrics of this sort are 
usually those which have a hole chucked through their center of 
throw. Such eccentrics are usually finished upon mandrels having 
two sets of centers. Fig. 149 shows such a mandrel. Work centers 



Fig. 149. General Shape of 
Eccentric 


10G 










































MACHINE SHOP WORK 


95 


A and A f are those to be used while the throw surfaces are being 
machined. B and B r the centers used while constructing the man¬ 
drel. With such a mandrel as this driven into the provided hole, 



work can be done upon surfaces which are concentric to the axis 
of the mandrel or which are eccentric with it. 

Using a Faceplate or Work Chuck. Eccentrics can and often 
are machined by mounting them upon a suitable faceplate or by 
holding the work in a suitable chuck. Previous to mounting 
the work upon the faceplate for eccentric turning, it is usual to 
face off a surface to set 
squarely on the front face 
of the plate, as in Fig. 151. 

Crank-Shaft Turning. 

This is a special kind of 
eccentric turning in which 
the throws are termed 
crank pins and the remain¬ 
ing bearings are the shaft 
proper. In Fig. 148 is 
shown a simple crank shaft 
with a crank pin G and 
regular bearings CD. 

It is customary to 
rough turn the bearings 
C and D previous to ma¬ 
chining the crank-pin bearing G. The order of operations is as 
follows: Locate, drill, and ream work centers in ends A and B. 
Square ends A and B to the correct overall length. Rough turn 
C and Z). Rough square E and F. Place attachments K and 
K on the ends of bearings C and D in position to machine crank- 
pin bearing G as shown. Rough turn G. Rough and finish square 



107 


















96 


MACHINE SHOP WORK 


II and I to gap dimensions. Finish surface G to dimensions. 
Remove attachments K and K and with work again mounted on 
centers A and B, finish square surfaces E and F, and finally finish 
to accurate dimensions surfaces C and D. 

Attachments K and K. These are often known as jigs and are 
made and used in a variety of forms. Those shown in Fig. 148 
are suitable for a single-throw crank, while those used in turning 
or grinding multiple-throw cranks may be circular in form and 
provided with several work centers. In all cases it means simply 
the provision of work centers opposite to and in alignment with the 
surface to be machined. It is self-evident that the same results 
can be obtained by casting or forging lugs or flanges upon the ends 
suitable for the various work centers. 

Handling Shaft Surfaces . In turning surfaces C and D, if the 
shaft is slender or of considerable length, use a center rest on surface 
D while working surface (7, to assist in its support and reverse for 
surface D. 

If necessary, struts may be placed between the jigs and cheeks 
of the shaft while machining surface G. In this manner, the whole 
piece may be steadied somewhat. 

Drive the w T ork, when surfaces C and D are being machined, 
with a common lathe dog. Use some sort of a faceplate stud when 
machining surfaces E, F, and G. 

Boring Bars. The boring of holes sometimes calls for a length 
and strength of tool that cannot be readily attained with the ordi¬ 
nary boring tool. A great deal of such boring is done with double¬ 
headed tools. These tools are held in bars, and cut at each end. 
An ordinary form of such tool is shown in Fig. 152. The tool A 
is turned and fitted so that when placed in the bar it is central with 
the centers of the latter. It is held in position by the key B . It 
cuts at each end. Such a tool may be made to do very rapid work. 
It is extensively used for boring in places where a piece of work 
must be duplicated a great number of times. 

Tools of this character are used for finishing. After the cut 
has been started, the tool should not be stopped until the cut has 
been completed. If it is stopped, there will be a ledge in the bore 
at that point. The reason for this is found in the springing of the 
metal and the contraction due to cooling while at rest. The tools 


108 


MACHINE SHOP WORK 


97 


used for finishing usually have a broad surface. Those used for the 
roughing cut are narrower; they wear more rapidly than the finishing 
tools, and are usually adjustable. An excellent example of the use 
of boring bars is found in the boring of engine cylinders. Special 
machines are used for such work. The greater portion of the work 
is done with a boring bar such as. that shown in Fig. 153. It con¬ 
sists of a heavy bar A, upon which there is a stiff traveling head B. 



The latter carries the tool C , which may or may not be capable of a 
transverse adjustment. The head moves longitudinally on the 
bar, and is held, adjusted, and fed by the screw D. At one end 
of the screw, there is a star wheel E , by which it is turned. As the 
bar revolves, one arm of the star strikes against a stop F at each 
revolution. This turns the screw by an amount proportional to the 
number of arms in the star. For example, if there are six arms 



Fig. 153. Special Boring Bar for Boring an Engine Cylinder 


in the star, the latter will be turned one-sixth of a revolution for 
each revolution of the boring bar. As the screw turns, it moves 
the head along the bar by an amount proportional to the pitch of 
its thread and the arms in the star. This forms the feed of the tool. 
For example, if a star has four arms, and is keyed to a screw of eight 
threads to the inch, then, for each revolution of the bar, the head 
will be advanced ^ of an inch. Another form of boring bar is 
shown in Fig. 154. 


109 


























98 


MACHINE SHOP WORK 


Boring bars with fixed tools are also used. In such cases the 
work is caused to travel beneath the bar as it is turned. A case of 
this kind occurs in the boring-out of brasses for railroad cars. 

In general, it may be stated that all metal work should be 
machined in the position which it is eventually to occupy. This is 
to overcome its tendency to spring out of shape under the influence 
of its own weight. In small articles this tendency is inappreciable. 
For large pieces it is sometimes quite apparent. 

Screw Cutting. The tools used for cutting threads are called 
screw-cutting tools. These tools are used in the lathe in the same 



Fig. 154. Boring Head 


manner as the diamond-point and round-nosed tools. The cutting 
edge of the tool must be of the same contour as the space between 
the finished threads. 

Types of Threads. There are five types of screw-threads 
commonly used in this country: the V-thread, shown in Fig. 155, 
has the form of an equilateral triangle, with an angle of 60 degrees. 
It is sharp at the top and bottom. This thread is difficult to cut, 
because of the trouble experienced in keeping the point of the tool 
sharp. 

The Sellers, Franklin Institute, or United States Standard 
is a modified form of V-thread, shown in Fig. 156. This thread 
has an angle of 60 degrees, with the top and bottom flattened for 
one-eighth of its depth. 


110 
















MACHINE SHOP WORK 


99 


Another form in common use is the square thread, shown in 
Fig. 157. The thread and space are of the same width. This 


Fig. 155. Section of V-Thread Fig. 156. Sellers, Franklin Insti¬ 

tute, or United States Standard 
Thread 

thread is used where heavy work is done, such as in jack-screws 
and presses. 

The Whitworth thread is similar to the United States Standard, 
the slight differences being as follows: the sides form an angle of 
55 degrees instead of 60 degrees, and 
the top and bottom are rounded instead 
of flat. 

The fifth type, the Acme thread, is 
somewhat similar to the square form. 

The difference is that the sides incline Fig 157 . xhread 
14§ degrees from those of the square 

thread. This form of thread is much used for lathe lead-screws and 
for giving motion to sliding parts of fine instruments, because the 
thread is simpler to construct than the square form, and the lost 






Fig. 158. Side View of Tool for 
Cutting Square Threads 


Fig. 159. 
Square Thread 
Tool Showing 
Inclination of 
Thread to Body 


motion can be taken up by simply closing the nut halves nearer 
together. 

Cutting Tool for Square Threads. The tool used for cutting 
square threads is shown in Figs. 158 and 159. It is of the proper 



ill 



















































100 


MACHINE SHOP WORK 


TABLE III* 

U. S. Standard Threads, Bolts, and Nuts 

The Tap Drill Diameters in the Table Provide for a Slight Clearance at the Root of the Thread 
in Order to Facilitate Tapping and Reduce Tap Breakages. If Full Threads Are Required 
Use the Diameters at the Root of the Threads for the Tap Drill Diameters Instead. 

U. S. Standard Screw Thread 

Pitch N 0 . 0 f Th’ds. per Inch 
Depth of Th’d. = 0.6495 XPitch 
Width of Flat=-?4^ 



i 

3 

Q 

Number of 

Threads 
per Inch 

Diameter 
at Root of 

Thread 

Diameter 
of Tap Drill 

Area in 
Square Inches 

Tensile Strength 

At Stress 
of 6000 Pounds 
per Square Inch 

Working Strength 
at Stress 
of 6000 Pounds 
per Square Inch 

Dimensions of Nuts 
and Bolt Heads 

of 

Bolt 

at Root 
of 

Thread 

0 


& 

a 

& 

1 

4 

5 

16 

3 

8 

7 

16 

1 

2 

16 

5 

8 

3 

4 

7 

8 

1 

li 

n 

it 

if 

if 

If 

if 

2 

2f 

2f 
' 2f 

3 

3f 

3f 

3f 

4 

4f 

4f 

4f 

5 

5f 

5f 

5f 

6 

20 

18 

16 

14 

13 

12 

11 

10 

9 

8 

7 

7 

6 

6 

f>2 

5 

5 

4f 

4f 

4 

4 

3f 

3f 

31 

3 

3 

2f 

2f 

2f 

2f 

2f 

2» 

2f 

2f 

0.185 

0.240 

0.294 

0.345 

0.400 

0.454 

0.507 

0.620 

0.731 

0.838 

0.939 

1.064 

1.158 

1.283 

1.389 

1.490 

1.615 

1.711 

1.961 

2.175 

2.425 

2.629 

2.879 

3.100 

3.317 

3.567 

3.798 

4.028 

4.255 

4.480 

4.730 

4.953 

5.203 

5.423 

1 

If 

U 

M 

3. 

if 

31 

T 2 

It? 

1 T 2 

iff 

iff 

iff 

iff 

iff 

2^ 

015 

"64 

2ff 

2 H 

015 

"T6 

3ff 

3! 

3f 

3ff 

4 T? 

4* 

4* 

4H 

5^ 

&T2 

5f 

0.049 

0.076 

0.110 

0.150 

0.196 

0.248 

0.307 

0.442 

0.601 

0.785 

0.994 

1.227 

1.485 

1.767 

2.074 

2.405 

2.761 

3.142 

3.976 

4.909 

5.940 

7.069 

8.296 

9.621 

11.045 

12.566 

14.186 

15.904 

17.721 

19.635 

21.648 

23.758 

25.967 

28.274 

0.026 

0.045 

0.068 

0.093 

0.126 

0.162 

0.202 

0.302 

0.419 

0.551 

0.694 

0.893 

1.057 

1.295 

1.515 

1.746 

2.051 

2.302 

3.023 

3.719 

4.620 

5.428 

6.510 

7.548 

8.641 

9.963 

11.340 

12.750 

14.215 

15.760 

17.570 

19.260 

21.250 

23.090 

160 

270 

410 

560 

760 

'1000 

1210 

1810 

2520 

3300 

4160 

5350 

6340 

7770 

9090 

10470 

12300 

13800 

18100 

22300 

27700 

32500 

39000 

45300 

51800 

59700 

68000 

76500 

85500 

94000 

105500 

116000 

127000 

138000 

260 

680 

1210 

1790 

2470 

3470 

4260 

5500 

6630 

7830 

9470 

10800 

14700 

18500 

23600 

28000 

34100 

40000 

45000 

50100 

58000 

66000 

74000 

82500 

93000 

103000 

114000 

124000 

If 

H 

25 

32 

1 

32 

If 

H 

iff 

2 

2A 

2f 

2;re 

2f 

2M 

3f 

3* 

3f 

4f 

4f 

5 

5f 

5f 

6f 

6f 

6f 

71 

7f 

8 

8f 

8! 

9f 

0.578 

0.686 

0.794 

0.902 

1.011 

1.119 

1.227 

1.444 

1.660 

1.877 

2.093 

2.310 

2.527 

2.743 

2.960 

3.176 

3.393 

3.609 

4.043 

4.476 

4.909 

5.342 

5.775 

6.208 

6.641 

7.074 

7.508 

7.941 

8.374 

8.807 

9.240 

9.673 

10.106 

10.539 

0.707 

0.840 

0.972 

1.105 

1.237 

1.370 

1.502 

1.768 

2.033 

2.298 

2.563 

2.828 

3.093 

3.358 

3.623 

3.889 

4.154 

4.419 

4.949 

5.479 

6.010 

6.540 

7.070 

7.600 

8.131 

8.661 

9.191 

9.721 

10.252 

10.782 

11.312 

11.842 

12.373 

12.903 

i 

4 

TS 

| 

16 

f 

fs 

8 

3 

1 

1 

1* 

If 

If 

if 

H 

H 

if 

2 

2f 

2f 

2f 

3 

3f 

3f 

3f 

4 

4f 

4f 

4f 

5 

5f 

5f 

5f 

6 

i 

19 

64 

ff 

li 

Tg 

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if 

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23 

32 

13. 

16 

29 

32 

1 

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1 16 

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4A 

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4& 


* Reprinted from Machinery. 


112 









































MACHINE SHOP WORK 


101 



Fig. 160. Diagram of Clearance Angle 


thickness at the cutting edge, but is somewhat narrower back of this 
point. T. he sides of the tool are inclined to the body, as shown at 
AB y big. 159; the amount of this inclination varies with the pitch of 
the thread and the diameter of the piece on which the thread is to 
be cut. To find the inclination, draw an indefinite straight line AC; 
and at right angles to it draw 
CD, Fig. 160. Make the length 
of CD equal to the circumfer¬ 
ence of the thread to be cut, 
measured at the root of the 
thread. On AC, lay off from 
C a distance BC equal to the 
pitch; then draw BD. This line 
will represent the angle of the 
side of the thread. The angle 
of the side of the cutting tool must be a little greater for clearance. 

Cutting Tool for Inside Threads. For cutting inside threads, 
the shape of the cutting edge of the tool should be the same as for 
cutting an outside thread, and the tool must be made so that the 
cutting edge alone touches the work. This is accomplished by 
bending the tool as shown .in Fig. 161, and giving it considerable 
clearance. 

Cutting Standard Screw-Threads . When screw-threads are to 
be cut, the pitch used depends upon the outside diameter of the 
bar. A standard which has been gen¬ 
erally adopted in the United States, 
is known as the United States Stand¬ 
ard. Table III gives the outside 
diameter of the screw from | inch to 
6 inches in diameter, with the num¬ 
ber of threads per inch to be cut. 

When setting the tool for any form of thread, the point of the 
tool must be exactly level with the centers, and a line at right angles 
to the axis of the lathe must bisect the angle of the tool point. In 
order that these conditions may be fulfilled, a thread or center gage, 
Fig. 162, is used. In this tool, the angles A, B, and C are made 
exactly 60 degrees. The two opposite sides are parallel. The 
angles A, B, and C are used when grinding and setting the tool. 



Fig. 161. Internal Threading Tool 


113 






















102 


MACHINE SHOP WORK 



1.1.111111111111111 iih 

Fig. 162. Thread or Center Gage 


The sides of the former are made to touch all along the edge of the 
tool. For setting the tool, the upper parallel side is held against 
the face of the work in a horizontal position. The tool is then 
set so that its sides touch along the edges of the notch B. The 

angle C may be used to gage the 
thread after it is cut. 

The pitch measurement of 
fine threads is a difficult matter 
where -an ordinary rule is used 
and the threads between the inch 
marks are counted; for this purpose pitch gages. Fig. 163, are very 
often used. The gages are short screw-sections on thin sheets of 
metal. To ascertain the pitch of any thread, set the gages over 
it successively until one is found that exactly fits. The figures 
stamped thereon will give the number of threads per inch. 

Lathe Adjustment for Cutting Threads. The cutting of a thread 
demands that there shall be a certain definite ratio of motion between 
the rotation of the work and the travel of the carriage. For example, 
if a screw having a pitch of \ inch—or with four threads to the inch, 
as it is usually expressed—is to be cut, the spindle must make four 
revolutions while the carriage is moving one inch along the bed. 

If the screw is to have 
eight threads to the inch, 
the spindle must make 
eight revolutions to each 
inch of motion of the 
carriage or tool; if six 
threads, then six revolu¬ 
tions to the inch of 
motion, etc. 

If, then, the apron 
lead-screw has four 
threads to the inch, it 
is evident that the speed 
of rotation of the spindle and of the screw must be the same, 
in order to cut a screw of four threads to the inch. In other 
w °rds, for each revolution of the lead-screw, the carriage moves 
the distance of the pitch of the same, or \ inch. Hence the gears 



114 




















MACHINE SHOP WORK 


103 


J and L, Fig. 95, must have the same number of teeth. When 
a screw of eight threads per inch is to be cut, the spindle must 
make twice as many revolutions as the lead-screw. Then, for 
each revolution of the spindle, the lead-screw makes half a revolution, 
and thus moves the carriage J inch. In this case, the screw gear L 
must have twice as many teeth as the stud gear J. For six threads, 
the ratio of revolutions between spindle and screw is 1J to 1. This 
requires 1J times as many teeth in the screw gear L as in the stud 
gear J. 

Selecting the Gears. The rule for finding the gears to be used 
on the spindle and lead-screw is: Multiply the number of threads 
on the lead-screw and the number of threads to be cut, by the same 
number; the products will equal the numbers of teeth on the gears 
to be used. 

Suppose the lead-screw has four threads per inch, and ten 
threads per inch are to be cut. Multiply both numbers by any 
convenient number, such as 6. Then the gears should have 24 
teeth and 60 teeth. 


Let a = Number of threads per inch on the lead-screw 
b = Number of threads per inch to be cut 
c = Any convenient number 
Then aXc = Number of teeth of gear on spindle 

bXc = Number of teeth of gear on lead-screw 
If. the gears thus found are not at hand, multiply by some other 
number. Thus, suppose gears of 60 and 24 teeth were not available; 
multiply 4 and 10 by any other number that would give the number 
of teeth of the gears at hand. 

Another way to find the gears is to remember that the number 
of threads to be cut is to the number on the lead-screw as the number 
of teeth on the screw gear is to the number of teeth on the spindle 
gear. 

EXAMPLES FOR PRACTICE 


1. The lead-screw has a pitch of \ inch. What is the ratio 
of gears to be used to cut a screw with 9 threads to the inch? If 
one gear has 24 teeth, how many should the other have? 


f 1:21 

\ 54 teeth 


115 


104 


MACHINE SHOP WORK 


2. The lead-screw has a pitch ‘of } inch. What is the ratio 
of gears to be used to cut a screw with 16 threads to the inch? 

Ans. 1:4 

3. The lead-screw has a pitch of J inch. What is the ratio 
of gears to be used to cut a screw with 12 threads to the inch? 

1 Ans. 1:4 

In these cases the actual number of teeth on the gears to be used is obtained 
by multiplying the ratio by some common multiple. Thus, in Example 1, 
multiplying by 10 gives 40 teeth for the stud gear, and 90 for the screw gear. 



Fig. 164. Simple Lathe Gearing Fig. 165. Compound Lathe Gearing 


In Example 2, multiplying by 20 gives 20 teeth for the stud, and 80 for 
the screw gear; and the same result is obtained by using the same multiple for 
Example 3. 

Every screw-cutting lathe is provided with a set of change 
gears from which selections can be made. In order to facilitate 
the choice of the gears to be used, a gear table, often cast in raised 
letters is screwed to the front piece of the headstock. This table 
shows the gears to be used for cutting such threads as may be listed 
in the table. 

Compounding Gears. It is sometimes necessary to cut a screw 
for which there are no gears which make a direct connection, in 


116 






MACHINE SHOP WORK 105 

which case the simple gearing shown in Fig. 164 cannot be used. 
Iliis necessitates the compounding of the gears on the intermediate 
spindle as shown in the set-up, Fig. 165. The spindle is represented 
by A and the screw by B. Suppose, with a lead-screw having 
three threads to the inch, it is desired to cut a screw having thirteen 
threads to the inch. This makes the ratio of teeth on the spindle 
gear to those on the screw 
as 3 to 13. The work can 
be done with spindle gears 
having 15, 30, or 45 teeth, 
with screw gears having 65, 

130, and 195 teeth, respec¬ 
tively. If it is found that 
. there are no gears having 
15, 45, 130, or 195 teeth on 
hand, compounding must be 
resorted to. To determine 
the gears to be used, it must 
be remembered that the 
product of the numbers of 
teeth of the driving gears 
must be to the product of the 
numbers of teeth of the driven 
gears , as the number of 
threads per inch on the lead - 
screio is to the number to 

be cut . In this case it is as 3 to 13. Multiply each of these figures 
by any convenient multiple. In the example in hand, let the mul¬ 
tiple be 200. Then, 

3X200 3X2X2X2X5X5 



13X200 13X2X2X2X5X5 


Select from the factors thus obtained two sets, each of which, when 
multiplied together, will give products equal to the number of teeth 
that are on hand. 

Thus, in the numerator, we may take 3X2X5, and 2X2X5, 
giving 30 and 20 as gears that are to be used as the spindle and 
intermediate drivers, respectively. 


117 








10G 


MACHINE SHOP WORK 


For the denominator, take 13X5, and 2X2X5X2, or 65 and 
40, for the driven gears of the intermediate stud and the screw, 
respectively. Placing these in position as in Fig. 166, we have 

Gear A with 30 teeth 
Gear C with 65 teeth 
Gear D with 20 teeth 
Gear B with 40 teeth 


EXAMPLE FOR PRACTICE 

It is desired to cut a screw with 11 threads to the inch on a 
lathe having a lead-screw with a pitch of \ inch. The gears avail¬ 
able have 30, 40, 45, 50, 55, 60, 65, 70, 80, 90, and 100 teeth, respec¬ 
tively. What ones are to be used, and where? 


Ans.< 


Spindle 

Intermediate driven 
Intermediate driver 
o Screw 


40 teeth 
55 teeth 
50 teeth 
100 teeth 


The following examples may be taken as applying to either 
right- or left-hand threads. The change or direction in the travel 
of the carriage is obtained by shifting the handle at its right center, 
Fig. 165, thus reversing the rotation of the lead-screw. 

The following description of the method of cutting a V-thread 
will suffice to illustrate the cutting of any form, with the slight 
changes which are necessary in the other forms because of the shape 
of the tool employed: 

First set the cutting point so that a line at right angles to the 
lathe axis bisects the tool angle, and so that the tool is exactly at 
the height of the center. 

The relation between the rotary motion of the work and the 
lateral movement of the tool, determines the pitch of the thread 
being cut; and the mechanism connecting the work and the tool 
must be of a positive character. 

Owing to the lost motion of backlash in the mechanism con¬ 
necting the tool and the work, the tool cannot be returned to the 
starting point for a new and deeper cut by simply reversing the lathe. 
The tool must first be withdrawn, the lathe reversed, the tool 
returned to the starting point, and then advanced for the new cut. 


118 



MACHINE SHOP WORK 


107 


To place the tool for the new cut with accuracy, a stop or graduated 
device is provided. 

When the work is removed from the lathe for testing, care should 
be taken in replacing, to get the tail of the dog in the same slot 
in the faceplate that was used to cut the original thread; this can 
be done by marking or otherwise indicating it. 

Hand=Chasing. The ordinary methods of cutting screws have 
already been described. Where great accuracy is not necessary, 
the threads may be chased by hand. A chaser, or chasing tool, 
differs from the ordinary thread-cutting tool, in that it has a number 
of cutting points instead of but one. When a chaser is operated 
by a power feed, it is customary to have a shaft revolve at the same 
rate or at an even multiple of the 
rate of the lathe spindle. This shaft 
carries a master thread into which 
a section of a nut drops. The 
handle connected with the nut car¬ 
ries the chasing tool. When the nut 
is in contact, the tool is cutting. 

At the end of the cut, the tool is 
lifted out, and with it the nut dis¬ 
engages with the thread. 

Hand-chasing requires a great 
deal of skill in order that a good 
piece of work may be done. The 
chasing tool has a number of points, 
as shown in Fig. 167. The work must be run rapidly in the 
lathe. The tool is held in both hands, and is supported on a 
rest similar to that shown for the hand-turning tools in Fig. 90. 
The first left-hand tooth of the chaser is brought lightly against 
the right-hand edge of the work. The handle is given a quick twist 
from left to right, throwing the teeth in the opposite direction. 
It is well, after the first twist, to stop the lathe and examine the 
work. If the operation has been properly performed, the second 
tooth will be found to have entered the groove made by the first. 
A short length of thread will have been cut out, the pitch being the 
same as that of the chaser. If this is correct, the lathe may again 
be started and the chaser applied as before. On the second trial 



Fig. 167. Hand Chaser Cutting 
Outside Thread 


119 
























108 


MACHINE SHOP WORK 



Fig. 168. Hand Chaser Cutting Inside Thread 


the thread may be run to its full length. The finishing of the thread 
is done by merely repeating the operation. A fine cut is taken with 

each application of the chaser 
for the whole length of the 
thread, until the full depth 
has been cut. In doing this 
work, the rear or right-hand 
side of the chaser should be 
pressed more firmly against 
the piece being cut than the 
front, because the threads w T ith 
which that portion of the tool 
is engaged are more deeply 
cut than at the front. In 
addition to cutting, these teeth also guide those in front. The 
reason for running the lathe at a high rate of speed, is that the 
movement of the chaser is less likely to be checked or thrown aside 
by seams or inequalities in the density of 
the metal than it would be if the lathe 
were to run slowly. Inside threading may 
be done by means of the inside chaser shown 
in Fig. 168. 

Drilling in the Lathe. The lathe can 
also be used for drilling. When such w r ork 
is to be done, the drill may be held in the 
spindle, and the work forced up against it 
by the screw of the tailstock; or the work 
may be revolved, and the drill forced in by 
the tailstock screw. When the first method 
is followed, the drill may be put into a 
socket prepared for it in the spindle of the 
lathe, or the drill may be held by a drill 
chuck, as show n in Fig. 169. This chuck 
may be used in the tailstock to hold twist 
drills, or to hold flat drills wdiich are forged 
from round stock. Flat drills made from flat stock are centered 
at the rear end, and held against, and fed forward by, the dead 
center. In this case, a slotted rest held in the tool-post, as in 



120 



































MACHINE SHOP WORK 


109 


Fig. 64, Part I, prevents the drill from turning, and aids in starting 
the drill true. 

When the drill is held in the headstock, the work may be fastened 
to the carriage and fed against the drill, or it may be held by means 
of a suitable device held in the tailstock. For this purpose the drill 



Fig. 170. Drill Pad for Flat Work 




> — 





Fig. 171. Drill Pad with V-Center for Holding Round Stock 


pad, shown in Fig. 170, may be used, especially if the work is flat. 
The V-center, shown in Fig. 171, is used when it is desired to drill 
through the axis of a piece of round stock. 

The shape of the groove prevents the work 
from turning; and the angle, being always in 
the axis of the lathe, determines accurately the 
location of the hole. 

DRILLERS 

Drilling Operation. Where holes are to 
be cut through metal using a rotating tool with 
the cutting edges at its point, the operation is 
known as drilling and the cutting tools are 
termed drills. These tools may be of the 
simplest type, as for example, Fig. 172, or 
they may be of the more elaborate type shown in Fig. 173, known 



Fig. 172. Flat Drill of 
Simplest Type 


121 



































110 


MACHINE SHOP WORK 


as a twist drill. While it is evident that any machine having a rotat¬ 
ing spindle may be used to drill holes, it is more usual to do this 
in a machine designed especially for and equipped to do this work. 

Drilling machines of the horizontal type are sometimes made, 
but the more common type is known as the vertical drilling 



Fig. 173. Typical Tapered Shank Twist Drill 



Fig. 174. Sensitive Driller 
Courtesy of Washburn Shops, Worcester, 
Massachusetts 


machine, often called a drill 
press. These have 1, 2, 3, or 
more spindles in a great variety 
of sizes, weights, and designs, 
many of which are made for 
purposes of special drilling only. 
The ones shown will be those of 
the kind commonly found in the 
ordinary machine shop 

While it is common practice 
to designate both the drilling 
machine and the cutting tool as 
drills, for convenience of descrip¬ 
tion in the accompanying text, 
the machine will be termed a 
driller and the cutting tool as a 
drill. It may also be said that 
this practice is meeting with 
general favor. 

Sensitive Driller. In Fig. 174 
is shown a drilling machine de¬ 
signed for use with the smaller 
sizes of drills on work under 
conditions which render it nec¬ 
essary to “feel” what the cut¬ 
ting lips are doing. It will be 
noticed that there are no trains 
of gearing present in the spindle 
driving mechanisms and that the 


122 















MACHINE SHOP WORK 


111 


tool is pressed or fed into the work by using the simplest and most 
direct device possible, a lever, a pinion and shaft, and a rack which 
engages the pinion. This is the simplest form of effective drilling 
machines and is known as a sensitive driller. In the cut, Fig. 174, 
B is the base, P the post, T the table, S the spindle, H the head 
bracket, C back-cone pulley, I the idler pulleys, A the spindle pulley, • 
and L the hand or feed lever. It will be noted that the construction 
permits the upper or square table to be swung out of position, 
allowing the lower or round table bracket to be put into a position 
for using this extra table and the crotch and cup centers. The 
nose of the spindle is bored out at its axis to what is known as a 
No. 1 Morse taper. Drills fitted with this taper can be used 
direct, or straight shank drills may be used in a drill chuck having 
a standard No. 1 Morse taper stem or shank to fit the spindle. 

Power Feed Driller. The heavier types of these machines are 
usually provided with back gearing similar to that employed in 
engine lathes. The power feed is obtained by suitable spindles 
and trains of gearing which drive the rack and sleeve by using a 
pinion, as in the hand feed machine. 

The essential differences between this machine and the smaller 
type are: (a) its heavy rigid frame and moving parts; (b) its range 
of spindle speed changes made possible by the cones and back gears; 
(c) its spindle feed by power gearing instead of a hand lever; (d) its 
greater spindle driving power gained largely by use made of the back 
gears; and (e) its sub-base for holding the heavier work. 

While the machine shown in Fig. 175 is belt driven, as relates 
to its stepped cone pulleys, the work spindle S is gear driven and 
gear fed. The trains of gearing, which rotate the spindle and which 
provide for feeding it downward, are, as in all modern geared 
machines, so covered as not to be plainly visible. The back gears 
are engaged at all times, but are brought into active driving service 
by operating a clutch B through use of the clutch lever C. The 
smaller spindle A passes downward through a cone of gears located 
in the gear box G to a train of gearing which is mounted upon the 
head bracket. The head bracket carries not only the work spindle 
sleeve and feed rack, but, besides these, has mounted on its frame 
the power and the hand feed mechanisms. The hand feed is oper¬ 
ated by rotating the hand wheel H. The power feed is controlled 


112 


MACHINE SHOP WORK 



Fig. 175. Standard Power Feed Driller 
Courtesy of Reed-Prentice Company, Worcester, Massachusetts 

by the clutch lever L. The changes of feed from fine to coarse are 
made by means of a slip key actuating the cone feed gears through 
the shaft E and the smaller hand wheel F. 


124 



















MACHINE SHOP WORK 


113 


Multiple Spindles. Drilling machinery, both horizontal and 
vertical, is sometimes provided with more than one spindle. In 
small vertical drillers of this description, Fig. 176, the spindles 
are fixed in their relative positions, and are not intended to be 
operated simultaneously; the work is passed from one spindle to 



another. The true multi-spindle driller is for the purpose of drilling 
several holes at one time and in any relative position within the limits 
of adjustment of the machine. 

Radial Driller. Another form of driller, known as the radial, 
is being extensively used. It is shown in Fig. 177. The drill spindle 
is carried on the arm A. It is so arranged that it can be set and 


125 









































114 


MACHINE SHOP WORK 


run at any position on this arm. At the same time, the arm may 
be swung around and clamped in any vertical or horizontal position 
about the upright B. These drillers are usually employed on heavy 
work w here a number of holes are to be drilled. 

In the case of the driller shown in Fig. 175, the work is usually 
light, and can be readily shifted so that the position of the holes 
can be brought beneath the drill. In heavy work, such as engine 



Fig. 177. Radial Driller with Four-Foot Arm for Heavy Duty 
Courtesy of Reed-Prentice Company, Worcester, Massachusetts 

cylinders, however, this cannot be done. It is therefore necessary 
to be able to shift the drill and place it in a position to do the work. 
The radial driller affords the means of doing this. 

Universal Radial . Where the vertical spindle carrying the 
drill can be rotated in the vertical plane, holes cannot only be drilled 
in any position, but also at any angle. Such a driller is called a 
universal radial. 


126 













MACHINE SHOP WORK 


115 


Laying Out. The position of the holes is usually laid out for 
the guidance of the man at the driller. The work is best done as 
shown in Fig. 178. The center punch mark, indicated by A, 
shows the location of the center hole. The circle upon which the 
prickpunch marks BBBB are placed, gives the location of the 
circumference of the hole. To drill the hole, place the point of 
the drill in the center punch mark A y and drill into the metal 
until the center punch mark has been slightly enlarged, as shown 
by the circle C . Then raise the drill and examine the w r ork. 
If the countersink, or hole whose circumference is indicated by the 



Fig. 178. Layout for 
Drilling Hole 



Fig. 179. Chiseling 
Countersink when 
not Concentric 


Fig. 180. Action of Groove 
in Making Drill Hole 
Concentric 


circle C, is exactly concentric with the outer circle BBBB , then 
the drill may be put down and the hole drilled. 

Owing, however, to various causes, it is not often that the 
circle will be concentric. This may be caused by one of three 
conditions, an uneven grinding of the drill; a distortion of the metal 
by the center punch; or an eccentric motion of the drill point, due 
to a lack of trueness in the running of the spindle. 

When the countersink is not concentric, the drill must be drawn 
back to the central position. The method employed is shown 
in Fig. 179. A round-nosed chisel is used to cut a groove E down 
the side of the countersink, on the side that is farthest from the 
circle BBBB . The depth of this groove depends upon the amount 
of eccentricity of the countersink and the depth to which it has 
been drilled. The drill is then run down again and the groove 
drilled out. The action of this groove is as follows: as the drill 


127 












116 


MACHINE SHOP WORK 


turns, one cutting edge is supported, and is working into the face 
C, Fig. ISO. At the same time, the cutting edge is opposite the groove 
E . The drill, therefore, springs into the groove, as shown. The 
lip then catches on the edge of the groove and cuts it away, making 
the hole elliptical, and shifting the center of the drill toward its 
proper position. As the drill sinks deeper, both lips are in contact 
with the faces C and D, and it has no further tendency to shift. 

When the groove has been drilled out, the drill must be again 
raised, to ascertain whether or not the countersink is concentric 
with the outer circle BBBB. If not, another groove must be cut, 
and the process repeated until the drill is correctly positioned, 
when the hole may be drilled. The prickpunch marks BBBB are 

put on the outer circle in 
order to indicate its position 
in case of the obliteration of 
the line itself. 

A twist drill will usually 
clear its hole of chips. For 
deep holes, this may not al¬ 
ways occur. It is then nec¬ 
essary to withdraw the drill 
and clean out the hole. This 
can be done by a piece of 
wire bent at the end; also by 
using a blowpipe made of a 
small tube, and bent to enter 
the hole, so that the chips will not blow up into the operator’s face. 
Holes in cast iron are more likely to need cleaning than holes in 
wrought iron or steel. Where flat drills are used, it is always nec¬ 
essary to clean the holes at frequent intervals, as such drills have 
no tendency to raise the chips and clear the holes. • 

Holding the Work. A matter to receive due consideration is 
that the work must be held rigidly on the work table while being 
drilled. This may be done in two ways. If the holes are to be 
drilled with great accuracy, the work must be clamped to the table. 
This is often done by means of straps, as shown in Fig. 181. In 
this figure, a gland A is shown clamped to the table by the straps 
BB. One end of the strap rests upon the flange of the gland and the 



Fig. 181. Work Clamped to Table by Strap for 
Accurate Hole-Drilling 


128 



























MACHINE SHOP WORK 


117 


other upon any convenient piece of metal C, of the proper thickness. 
The bolt D is put up through a hole in the table as close to the 
work as possible. When the nuts are screwed down, they then put 
the greatest available pressure on the work, and hold it fast. The 
strap B is made of flat iron. It has one or more holes drilled in it 
to permit the passage of bolts. 

Another method of holding work in the drill press is by means 
of a post. This is shown in Fig. 182. It consists of a post A, set 
loosely in one of the holes in the table. As the drill is forced against 
the work, it tends to turn the latter with it. When the work strikes 
the post, it is stopped and held while the hole is drilled. This will 
not hold the work perfectly steady. It allows the latter to move 
with the eccentricity of 
the motion of the drill, 
but it is in very common 
use where extreme accu¬ 
racy is not essential. For 
example, where a finished 
bolt is to be used with 
a driving fit, the work 
must be securely fas¬ 
tened so that the diam¬ 
eter of the hole may be 
true. Where a machine 
bolt made of rough iron 
is to be used, the hole is drilled ^ inch larger than the normal size 
of the bolt. Here accuracy is not even attempted; a variation of 
inch in the diameter of the hole is of no account. Therefore, in 
such cases, the work may be allowed merely to rest against the post. 

This question of holding the work does not apply to drills of the 
multi-spindle class. It is evident that the tendency of one drill to 
rotate the work is counteracted by the action of another drill. 

An angle iron forming a right angle with the work table, is 
used in many cases to support the work where the hole cannot be 
properly located by the use of the table alone. The clamping of 
the work to the angle iron must be very rigid to resist the pressure 
of the drill. A tilting table is sometimes used, so that the holes 
may be drilled at any required angle. At least one manufacturer 



129 


















118 


MACHINE SHOP WORK 


is putting on the market a horizontal drilling machine which can 
drill five sides of a cube at any angle, with but one setting of the work. 

Tapping. Drilling machines may also be used for tapping. 
This requires a reversing device for backing out the tap. The back¬ 
ing-out is done at a much higher speed than the tapping. The tap 
is held in a friction head that will slip when the tap strikes the 
bottom of the hole. The use of collapsing taps, especially on 
diameters of one inch and over, renders the backing-out unneces¬ 
sary, and quickens the operation. Studs may be set by the same 
device, so that cylinder flanges may be drilled, tapped, and the studs 
set, without removing the work from the machine. Duplicate 
drilling by means of jigs will be considered later. 

PLANERS 

As the name indicates, the planer is used for finishing flat 
surfaces. In the ordinary planer, the w T ork is moved, and the tool 
is at rest. A common form of this tool is shown in Fig. 183. It 
consists of a bed A, upon the upper surface of which suitable guides 
or ways are planed. The platen B is made to travel back and forth 
upon these ways. The platen has a rack on its under surface, into 
which the gear C meshes. This gear is driven by a train of gears 
from the shaft carrying the pulley D. The tool is carried on the 
tool-head E> where it can be given a slight vertical motion or feed. 
This tool-head may be fed across the machine by the screw in the 
cross-rail F . The latter may be raised and lowered by the shaft 
and gearing shown at the top. This gearing turns two vertical 
screws running in nuts attached to the cross-rail. 

The reciprocating motion of the planer table is obtained as 
follow’s: The pulleys D and G run loose on the shaft, and are driven 
in opposite directions by belts from an overhead countershaft. The 
center pulley is fixed to the shaft, and either belt may be moved over 
on this pulley by the belt-shifters J, which are moved in opposite 
directions by a connection with the shifting lever I, connected with 
them by suitable mechanism inside the bed, and acted upon by the 
reversing dogs H H y which are adapted to be adjusted at any point 
in the length of the table, according to the position of the work and 
the length of the stroke desired. 


130 


MACHINE SHOP WORK 


119 


The planer shown in Fig. 183 has but one head for holding a 
tool. In large planers it is customary to have two heads on the 
cross-rail, so that two tools may be cutting simultaneously, thus 
doubling the capacity of the machine. The vertical feed of the tool 
is also operated automatically; and in a planer having two heads, 
both vertical and lateral feeds are independent of each other. 



Fig. 184 shows a large planer equipped with two heads on the 
cross-rail, and a still further equipment of two heads with automatic 
vertical feeds on the side posts. Thus arranged, the machine is 
capable of handling very large work, and of keeping four tools 
cutting simultaneously. The table-operating mechanism within the 
bed is substantially the same in nearly all except some special planers. 
In this planer, there is a driving belt on each side of the machine, 
one running the table forward, and the other backward, the rod 
carrying the belt-shifters passing entirely through the machine. 


131 



































• ■ 

120 MACHINE SHOP WORK 



132 


Fig. 184. Large Planer* with Two Heads on Cross-Rail and Two Heads on Side Posts 
Courtesy of Cincinnati Planer Company, Cincinnati, Ohio 






MACHINE SHOP WORK 


121 


The speed of travel forward of the table is the ordinary cutting 
speed; while, to save time, the return or backward movement is as 
fast as the driving mechanism will permit. The ratio of forward 
to backward speeds will be from 2 to 1 (in very large planers), to 4 
to 1 (in small planers). 

Ordinarily the tool cuts only when the platen is moving toward 
the right, Fig. 183. As a result of this condition, the platen is 
made to move more rapidly toward the left than toward the right. 
This is accomplished by varying the speeds of the pulleys D and G. 
The usual ratio of the speeds of these pulleys is 2 to 1 or 3 to 1. 

The feed of the tool is accomplished by a friction clutch driving 
the vertical rack K. This acts only at a point near the end of the 
travel of the platen. It is so arranged that any reasonable vertical 
or horizontal feed may be 

given to the tool. Jrjft 

The machine is driven 
by three driving pulleys n. 

placed side by side on the / / X I 1 

same shaft, the central V/ Iji Sij ||" 

one of the three being ^— -^J x Mlllflih, Ik /hi 1 lilt 

keyed to the shaft. The \\ 1 11 11 1 .1 l lM lII 

reversal of the motion of lg5 L at h e Tool Improperly Set Up 

the platen is obtained by 

shifting one or the other of the belts onto the central pulley. 

Planer Tools. The tools used with planers do not differ essen¬ 
tially from those described for lathe work. The same rules apply 
regarding the holding of the tool. It should project as short a dis¬ 
tance as possible beyond the point of support. When there is an 
excessive projection, care should be taken that the tool is so set 
that it will not spring into the work. On the lathe this can be 
prevented by setting the point of the tool on a line with the center. 
In Fig. 185 the tool tends to spring and turn about the point A as 
a center. The dotted line at the point shows how this tends to throw 
it into the work. The same thing is shown in the planer tool in 
Fig. 186. This tendency can be overcome by forging the tool so 
that the cutting point is behind a perpendicular from the point of 
support, as shown by the dotted lines in Fig. 186. In the latter 
jcase, the spring of the tool tends to take it out of the work. 


133 












122 MACHINE SHOP WORK 

Holding the Work. The work is usually held on the planer by 
clamping it down with straps in a manner similar to that shown 
in Fig. 181. Where the whole upper surface is to be planed over, 

holes are sometimes drilled in the 
sides, into which the rounded ends 
of straps are set. 

Fig. 187 shows the manner of 
clamping down a machine bed A, 
by the use of straps BB having 
the ends bent downward so as to 
avoid the use of the loose blocks C 
as shown in Fig. 181. In addition 
to the straps, there must be plugs 
C placed in the circular holes in 
the planer table, which take the 
thrust due to the action of the 
cutting tool, and prevent the bed 
A from moving on the table. In 
planing the pedestal D, it will be 
necessary to provide still further support, which is done by the 
brace E, placed against the plug F, and adjusted to the proper 
length by the screw and check-nut at e. 

It is impossible to give more than general directions for clamping 
work on a planer. A great variety of blocking, clamps, and bolts 




Fig. 187. Method of Clamping Down Planing Machine Bed and Supporting Work 


may be used, such attachments being suited to the work in hand. 
It should be sufficient to say that the work must be carefully set, 
strongly clamped and braced to prevent movement by the tool; 
and the clamping should not distort the work. As all castings 


134 




















MACHINE SHOP WORK 


123 


and forgings change their shape when the surface is removed, it is 
considered good practice to release the clamps before the finishing 




Fig. 189. Planer Chuck for Holding Work 



Fig. 190. Planer Centers 


cut, in order that the piece may assume its final shape, and then 
reclamp it without distortion. 


135 













































































































124 


MACHINE SHOP WORK 


Angle irons or knees, as shown in Fig. 188, may be considered 
as an auxiliary table with a surface at right angles to the main table. 
Many useful applications of these holding devices will suggest 
themselves. 



Another method of holding work is by using a planer chuck , 
such as is shown in Fig. 189. In use the chuck is bolted to the platen, 
and the work is held between the chuck jaws. 

Planer centers, as illustrated in Fig. 190, are very useful in 
machining parts where accurate circular spacing is desired, or where 
projecting lugs prevent the work surface turning in a lathe. 


136 







MACHINE SHOP WORK 


125 


Plate Planer. A special form of planer extensively used in 
boiler shops and shipyards is the plate planer, Fig. 191. It is used 
for planing the edges of long plates. The plate is securely fastened 
between the 12 pneumatic jacks and the bed. The tool is held in 
the carriage seen in the , center, which is moved to and fro by the 
screw, which in turn is driven by the electric motor through the 
gearing at the left. For starting, stopping, and reversing the direc¬ 



tion of the carriage, a shifting rod is arranged along the front of the 
machine, as shown in the illustration; handles may be moved to 
positions of convenience for the operator while working on plates of 
various lengths. The tool holder is so arranged that by the use of 
one tool, a beveled or a straight cut may be taken in either direction. 
On the saddle is carried a platform from which the operator may 
have a constant view of the tool. 


137 

















































126 MACHINE SHOP WORK 

SHAPERS 

For the lighter jobs of planing, the shaper, or shaping planer, 
Fig. 192, is extensively used. It possesses the advantage of rapidity of 
action. In this machine, as in the plate planer, the tool reciprocates 
while the work is at rest. A suitable mechanism causes the ram 
A. to move to and fro. When moving toward the left, the tool is 



cutting. As in the ordinary planer, the speed of the cutting stroke 
is less than the return. 

The piece is held on the work table B, which may be adjusted 
to any convenient height suited to the work being done. The tool 
is also allowed a limited vertical adjustment in the slide by turn¬ 
ing the handle C. This is the ordinary method of obtaining the 
vertical feed. 

The horizontal feed is obtained by moving the table B sidewise. 
In some shapers it can be moved vertically to feed to or from the 
tool; in other machines the horizontal feed is obtained by causing 
the tool with the reciprocating parts to move sidewise. 


138 







































MACHINE SHOP WORK 


127 


The style of machine shown in Fig. 192, is called the pillar 
shaper; but where the tool and ram move sidewise, it is called the 
traverse shaper, Fig. 193. The character of the work done 




Fis- 194. Vertical Slotter 


on the shaper is the same as that done on the planer; but as a rule 
the shaper is used for the smaller and more delicate parts which 
could not be handled quickly on the planer. The shaper has the 
additional advantage of a change of speed, which allows small 


139 



































128 


MACHINE SHOP WORK 




Fig. 195. Bar 
for Slotting 
Locomotive 
Trains 



Fig. 196. 
Slotting Tool 
for Cutting 
Keyways 



Fig. 197. 
Slotting Tool 
with Large 
Rake 


pieces, especially of the softer metals, to be machined 
at a maximum rate. 

Slotter. Another machine tool which is not used 
as commonly as its many good qualities would seem 
to warrant, is the slotter, Fig. 194. It is in reality a 
shaper with the tool reciprocating vertically instead 
of horizontally. It is used for working on heavy 
pieces, and especially in places where an irregular 
contour is to be formed. The thrust on the tool is 
vertical, and it and the machine must be very stiff. 
The work done frequently partakes of the nature of 
forming the inside of the hole where the tool must 
project the whole length of the cut below the bottom 
of the head. Such a case is that of the slotting of 
locomotive frames. The best type of tool for such 
a class of work is a strong bar, as shown in Fig. 195. 
The bar is held in the head of the tool, just as any 
tool would be. Near the lower end, it carries the cut¬ 
ting tool, which may be fastened by a set screw or 
wedge. Such a tool should always be used when it is 
possible. It has the advantage of being stiffer and 
less likely to spring than a common forged tool. 

The tool used in a slotting machine differs from 
that used in the lathe or planer, in that the direction 
of the cutting motion is different. Fig. 196 illustrates 
a slotting tool used for doing such work as the cut¬ 
ting of keyways in the hubs of pulleys. It will be 
seen that if the tool is moved in the direction of the 
arrow, the face B becomes the one against which 
the chip bears. It therefore corresponds to the top 
of the lathe tool. The sharper the slope givefi to the 
face B, the keener the edge, just as increasing the top 
rake of the lathe tool increases its sharpness. The 
face A must also be cut away as indicated. This 
corresponds to the clearance of the lathe or planer 
tool. It is quite impossible, at times, to give these 
tools a larger amount of rake. Such a form is shown 
in Fig. 197. The shape of this tool is such that it is 


140 















MACHINE SHOP WORK 


129 


very strong in the direction of the thrust, besides having a keen 
cutting edge. 

The slotter has automatic feeds of three kinds—namely, lateral, 
transverse, and circular—hence a considerable variety of work can 
be done upon it. The stroke of the vertical ram which carries the 
tool can be changed to any length from zero to the full stroke, and 
its location with relation to the work table can be adjusted according 
to the height of the work to be done. Like the shaper, it has a quick 
return after the cutting stroke, and it is provided with four changes 
of speed. This renders it available for quite a large range of work. 


141 














MACHINE SHOP WORK 


PART III 


POWER=DRIVEN TOOLS -(Continued) 

MILLING MACHINES 

Milling Machine vs. Shaper and Planer. The operation known 
as milling differs so radically from the removal of metal by methods 
previously described, that it merits much more careful and lengthy 
discussion than has been devoted to the other methods. Owing, also, 
to its increasing importance and general use, it calls for a some¬ 
what detailed discussion. While milling is coming rapidly into favor 
as a means of doing work formerly done on the shaper and planer, 
it does not follow that the shaper and planer are to be entirely 
abandoned. There has been a tendency to belittle the planer and 
shaper in favor of the milling machine. This tendency is not 
altogether warranted even by the rapid and economical method of 
milling. There is a large class of work which can be done as accurately 
—and in many cases as cheaply—by means of a single-pointed tool 
such as is used in the planer and shaper. 

Simple Milling Operations. The fundamental difference between 
planing and milling lies in the character of the tool employed. The 
planer uses a fixed single-pointed tool, with a reciprocating motion 
either of the tool or of the work. Milling is performed by the use 
of a rotating tool with several cutting points. This rotary multiple 
cutter is the basis of all milling operations; and, as the saw may be 
taken as a good example of such a cutter, so the work done by the 
circular saw in cutting metal may be said to be an example of milling, 
Fig. 198. The ordinary milling cutter is nothing more than a saw 
which has exceptionally broad teeth and in which the contour of the 
cutting blades is made to suit the work in hand. 

It was but a step to make a saw wide enough to cover a con¬ 
siderable surface, or to have a thick saw with a suitably formed 
cutting edge. Several saws of different shapes and sizes can be 


143 



132 


MACHINE SHOP WORK 


mounted in a gang on an arbor, and perform operations which it 
would be hard to duplicate on the shaper or planer. Even in the 
present age of special machines for milling, a great deal of work of 
this character is still performed by the method indicated. 



Fig. 198. Sawing Flat Stock 

Courtesy of Brown and Sharpe Manufacturing Company, Providence, Rhode Island 

One of the great advantages of milling is the certainty of exact 
duplication—a feature of prime importance in the manufacture of 
interchangeable work. 

About the first machine built exclusively for milling was the 
so-called Lincoln miller, Fig. 199, which consists essentially of a bed 


144 















MACHINE SHOP WORK 


133 



carrying the equivalent of the headstock and tailstock of a lathe, 
with means for rotating the cutter arbor, which is carried directly 
by the headstock spindle, and steadied and supported by the tail- 
stock. There is also provided a table upon which the work can be 
fastened either directly or by means of a vise; and an automatic feed 


Fig. 199. Lincoln Milling Machine 
Courtesy of Pratt and Whitney Company, Hartford, Connecticut 

across the machine at right angles to, and below, the cutter arbor. 
This type of machine in various designs is much used in modern 
manufacturing. 

MILLING CUTTERS 

Classification. As the type of cutter used determines, in a large 
measure, the design of the machine itself, it will be better at this 
point to take up a description of some of the different cutters, 


145 








134 MACHINE SHOP WORK 


in order that the adaptation of the machine to the cutter may be 
clearly seen. 

Cutters are classified according to their form or the use to which 
they are put, some of the more common types of these devices being 


as follows: 

1. Slitting 

2. Grooving 

3. Fluting 

4. Straight 

5. Angle 

6. Double-angle 

7. Straight mill 

8. Spiral mill 

9. Nicked-tooth spiral mill 

10. Side mill 


11. Straddle mill 

12. Straight end mill 

13. Spiral end mill 

14. T-slot mill 

15. Formed mill 

16. Inserted blade 

17. Inserted-tooth facing 

18. Inserted-tooth surfacing 

19. Shell mill 

20. Fly or single-tooth cutter 


This classification does not include any of the cutters used in 
cutting gears, racks, spirals, helical gears, ratchets, sprocket-wheels, 



and similar work, which is usually considered as gear-cutting work. 
However, ratchet teeth may be cut with an angle cutter; brass gears, 
with a single-tooth or fly cutter, properly formed; and some others 
may be applied to a variety of uses, the cutter, in fact, not infre¬ 
quently displaying a remarkable adaptability to the varying 
conditions of work and material. 


146 






















MACHINE SHOP WORK 


135 


Fundamental Characteristics. The several details of an ordinary 
milling cutter are shown in Fig. 200. A is the outside diameter; 
B } the thickness (or in mills such as shown in Fig. 201, the length); 
C, the diameter of 
the hole; D, the 
width of keyway; E, 
the depth of keyway; 

F t the pitch of the 
teeth; G, the top of 
the teeth or land; H f 
the backing-off or 
clearance, either on 
the lands or on the 
side of the cutter; 

J, the depth of the 
teeth; K, the face of 
the teeth; L, the relieving recess made for the purpose of reducing 
the surface to be ground; and M, the hub. The direction of revolu¬ 
tion is indicated by the arrow. 

Cutter Arbor. Fig. 202 shows the usual form of cutter arbor, 
in which A is the taper shank fitting the taper-reamed hole in the 
milling-machine spindle; B is the flattened portion or tang fitting in 
the cross-slot and preventing the arbor from turning; C is a nut used 
in withdrawing the arbor from the hole when it has been forced tightly 
into it; D is a collar formed upon the arbor, against which loose 
collars or the cutter itself are forced when placed upon the arbor at 
E and confined by the clamping nut F. The end G is finished as a 


Fig. 202. Ordinary Form of Cutter Arbor 

journal or bearing for an outer support attached to or forming a part 
of the overhanging arm of the milling machine. In the outer end is 
drilled and reamed a center hole for a similar purpose. 

Fastening Cutter in Arbor. Cutters are prevented from turning 
upon the arbor in any one of four ways namely, first, by a key 
in the key way BE, Fig. 200; second, by being clamped between 





Fig. 201. Milling Cutter with Spiral Teeth 
Courtesy of Brown and Sharpe Manufacturing Company, 
Providence, Rhode Island 


147 







136 


MACHINE SHOP WORK 


loose collars on the arbor; third, by being threaded and screwed on 
the arbor; and fourth, when the cutter is quite small and the work 
light, by a large-headed screw, slotted for the screwdriver, and tapped 
into the end of the arbor. In the latter case, the thread must be 



Fig. 203. Screw-Slot Cutter 



Fig. 204. Slitting Saw 


right- or left-handed, according to the direction of revolution, so that 
the torsional strain of the work will tend to keep the cutter screwed 
tightly against the shoulder. 

Usually cutters are made right-handed; that is, if held so that 
the side which goes against the collar on the arbor is toward the eye, 
the cutter should turn in the same direction as the hands of a clock. 

Locating Position of Cutter. To locate the cutter in the proper 
position on the arbor to suit the work to be done, loose collars of 
various thicknesses are used on the arbor, placing as many on each 



Fig. 205. Plain Milling 
Cutter 



Fig. 206. Spiral Cutter with Nicked Teeth for Heavy Cuts 
Courtesy of Becker Milling Machine Company, 

Hyde Park, Massachusetts 


side of the cutter as are necessary to fill the space between the fixed 
collar D, Fig. 202, and the clamping nut F. The cutter and loose 
collars must have smooth, true, and parallel faces; otherwise the 


148 




MACHINE SHOP WORK 


137 


arbor will be sprung when the clamping nut is screwed up, and will 
not run true. 

Plain Milling Cutters. Screw-slotting cutters, Fig. 203, and 
slitting saws, Fig. 204, are saws of a special type. The true milling 
cutter, Fig. 205, has a face much wider in proportion to its diameter 
than the common slitting saw. It is for the production of surfaces, 
rather than for a thin saw kerf in separating pieces of metal. These 
plain cutters are made in a large number of diameters and lengths, 
and are all designed for the generation of plane surfaces. 

Spiral Cutters with Solid or Nicked Teeth. As we have seen in 
the case of reamers, heavy cuts can be taken more easily when the 



Fig. 207. Side Milling Cutters Mounted 
as a Heading or Straddle Mill 



Fig. 208. Interlocking Cutter with 
Four Teeth Cut Away 
Courtesy of Union Twist Drill Company, 
Athol , Massachusetts 


chip is broken up in small pieces; therefore, in milling cutters designed 
for roughing, it is customary to nick the teeth, Fig. 206, in such 
a way that the stock left by one tooth may be taken out by the 
following tooth. This makes the cutting easier. A plain cutter of 
any considerable length, with teeth formed by straight grooves, will 
not often make a smooth surface because of the varying pressure of 
the cutter as one tooth after another leaves the work. To avoid 
this springing tendency, cutters are made with spiral teeth, Fig. 203, 
either right- or left-hand, so that there is practically a uniform dis¬ 
tribution of pressure at all points during the cut. 

Side Milling Cutters. When it is desired to mill the side of a 
piece, it is necessary that there should be teeth on the side of the 


149 













138 


MACHINE SHOP WORK 


cutter. Such cutters are usually made comparatively narrow and 
with teeth on both sides, as shown in Fig. 207. These side milling 



Fig. 209. Gang Cutter 


cutters are often sold in pairs. When mounted together, as in 
Fig. 207, they are often used to mill off both sides of a piece of work, 



Fig. 210. Forms of Angle Cutters 


as, for example, a bolt-head; and they are therefore called heading 
or straddle mills. 


150 







MACHINE SHOP WORK 


139 



Interlocking Cutters. If two cutters of the same diameter are 
mounted together, it is difficult to mill a surface which will not show 
the line of separation of the cutters. This can be avoided by making 
the ends of the cutters, where they come together, of such a shape that 
they interlock one with the other. This feature of interlocking, 
Fig. 208, is especially valuable when cutting slots which must be of 
a definite width. An ordinary cutter will wear away by use or by 
grinding, and thus lose its correct size. The thickness of the inter¬ 
locking cutters can be maintained, however, by means of very thin 
washers; and, owing to the 
interlocking of the cutters, 
no space will show between 
them. 

Gang Mills. Cutters 
may be mounted in gangs 
of great variety and com¬ 
bination, a typical one 
being shown in Fig. 209. 

These cutters may be of 
any desired form, and can 
be made to produce a 
variety of shapes. 

Angle Cutters. The 
so-called angle cutters, 

Fig. 210, are often em- Fig. 211. Cutter with Inserted Teeth 

. 1 . , e u. Courtesy of Becker Milling Machine Company, 

ployed 111 the manufacture Hyde Park , Massachusetts 

of other milling cutters. 

When used in making spiral cutters, they must have an angle on both 
sides, the customary angles in such cases being 40 degrees, 43 degrees, 
45 degrees, and 48 degrees on one side, and 12 degrees on the other. 
The common single-angle cutters vary from 40 degrees to 80 degrees, 
either right- or left-hand. Double-angle cutters, as shown in the 
center of the lower row, Fig. 210, can be had with either 45 degrees, 


60 degrees, or 90 degrees included angle. 

Inserted=Tooth Cutters. Only such cutters as are made from 
a single piece of tool steel have been so far considered. In large 
cutters, however, the cost of the steel becomes an important item, and 
there is the ever-present danger of losing a large amount of labor 


151 


140 


MACHINE SHOP WORK 


by breakage when hardening. To make an economical, serviceable 
cutter of large size, it is customary to use a cast-iron body with 
inserted tool steel teeth. There are several different methods of 
inserting and holding these teeth. Usually, when the inserted tooth 



Fig. 212. Form of Inserted-Tooth Cutter Called Slabbing Cutter 


is in the form of a blade, they are held by taper pins or screws, 
Fig. 211. These blades are renewable, the cast-iron body being used 
many times. 

Another form of inserted-tooth cutter consists of round, hard¬ 
ened steel pins driven into holes in a cast-iron body. This cutter is 
also permanent in form, Fig. 212, as broken teeth cannot be replaced; 
and, when the teeth are worn almost down to the body, the whole 
cutter is thrown away. 

Form Cutters. Brief mention has been made of cutters to 
generate irregular contours. These cutters are known as form 
cutters, and, except in certain shapes, such as quarter- and half- 
rounds, are not carried in stock, but are made only to order. There 
is such a large variety of forms for which such cutters may be used 



Fig. 213. Gang of Form Cutters 


that it is impossible to give more than typical examples. The 
form shown in Fig. 213 consists in reality of several cutters, some of 
them of ordinary shapes and sizes, with others of special forms, the 
whole making a gang cutter whose object is very apparent. 


152 














MACHINE SHOP WORK 


141 


Among the standard shapes of form cutters are some which 
are now carried in stock for producing certain tools requiring cutters 
of definite yet peculiar form. Among these may be mentioned cut- 



Sprocket Cutters. 




ters for fluting taps, reamers, and twist drills; cutters for sprocket 
and gear teeth; and cutters known as hobs, for the production of 
worm gears, Fig. 214. 


153 


























































142 


MACHINE SHOP WORK 


End Mills. All the cutters thus far mentioned are provided 
with central holes, and are intended to be mounted on an arbor 



Fig. 215. Ordinary Form of End Mill 
Courtesy of Becker Milling Machine Company, Hyde Park, Massachusetts 


which is carried by the milling machine spindle and supported in 
some suitable manner at the outboard end. There is an entirely dif¬ 
ferent class of cutters, 

r 


however, w T hich are sup¬ 
ported by the spindle 
only, and which are pro¬ 
vided with teeth at the 
end of the cutter. These 
are known as end mills. 



Fig. 216. T-Slot Milling Cutter and Section of Slot 


They are made in a great variety of shapes and sizes, the ordinary 
end mill, Fig. 215, being cylindrical, with either a right- or left- 


hand spiral. 

T-Slot Cutter. A special 
form of end mill for making 
T-slots is called the T-slot cut¬ 
ter, and is, in reality, a small 
side milling cutter carried by a 
small central stud, as shown in 

Fig. 216. 




Fig. 218. End Mill with Inserted Teeth 
Courtesy of Becker Milling Machine Company, 
Hyde Park, Massachusetts 


Dovetail Cutters. Dovetail cutters, Fig. 217, and cutters of various 
angles for making ratchets, are merely variations of the end mill. 


154 
























MACHINE SHOP WORK 


143 



Fig. 219. Taper Collet 


When end mills are made of large size, they can be furnished 
with inserted teeth, Fig. 218, similar to those described. The 
heaviest end mills for 
the milling machine 
are sometimes made 
as large as fifteen to 
twenty inches in diam¬ 
eter, the cast-iron body being screwed directly onto the nose of the 
spindle, making a very powerful and fast-cutting tool. 

Methods of Mounting Milling Cutters. The plain milling cutter 
is mounted on an arbor in a way very similar to that in which its 
spindle, prototype, the circular saw, is mounted. 

Where the cutter teeth are formed integral with, or fastened to, 
the taper shank, as in the case of end mills, the shank, if it be of a 
proper size, is placed directly into the taper hole in the spindle. 
In many cases, however, the taper shank of the cutter is much too 
small to fit the spindle hole; and taper collets, Fig. 219, are used to 
bush down the spindle hole to the proper size. Of course, it is 
necessary that the axes of the outer and inner tapers should coincide; 
otherwise the cutter will 
not run true. In some 
cases it is necessary 
to use two collets, one 
within the other, before 
introducing the cutter 
shank. 

When shell end mills, 

Fig. 220, are used, a 
special form of taper 
shank is employed which 

_ 1 1 -n* , Fig. 220. Shell End Mill and Taper Shank for Holding It 

can take several dmerent 

sizes of cutters. The construction is so obvious from the illustration 
that explanation is unnecessary. 

End mills, having taper shanks, rely largely on the friction of 
the taper for holding in position, although being driven by a tongue 
at the end of the shank. Therefore cutters of this description should 
not have a spiral in a direction which would tend to pull the cutter 
out. This is not a serious objection when using the cylindrical portion 



155 











144 


MACHINE SHOP WORK 


of the cutter; but when using the end of the cutter, it means that the 
teeth can have no rake, and must scrape rather than cut the work. 
In order to use a leading spiral on the cutter, the shank must be held 
positively in the spindle. This usually is accomplished by inserting 
in a threaded hole at the rear end of the shank, a rod which extends 
through the hollow spindle and brings up against a collar on the out¬ 
side. This can be set up solidly, and all danger of loosening-up of 
the cutter shank will be avoided. 

When the cutter is small, as compared with the diameter of the 
spindle taper, a screw collet may be used, as the friction of the collet 

will be greater than the tendency of 
the leading spiral to move the cutter 
from the spindle. These screw collets 
are commonly made of machine steel, 
while the end mills are made from 
tool steel. The short, steep taper 
and threaded end are shorter than 
the long taper shank, resulting in a 
cheaper cutter. 

One of the best means for hold¬ 
ing small end mills with straight 
teeth is by the use of spring collets, 
Fig. 221, which can firmly grasp the 
straight shank of the cutter. When 
cutters are to be changed frequently, 
this is a particularly satisfactory 
method, although it will not answer for roughing cuts where cutters 
of large diameter are used, as the torque will be too great for the 
jaws of the collet to prevent turning. 

An ordinary drill chuck can be held in the spindle by means of 
a taper shank, and furnish a means of holding straight-shank drills 
and other small straight-shank tools. 

A very convenient method of holding certain tools consists in 
fitting a three-jawed universal lathe-chuck to the threaded nose of 
the spindle, thus enabling straight-shank tools of large size to be held 
firmly and accurately. Cutters of any kind are rarely held in chucks 
on the milling machine, but a large number of other small tools can 
be held advantageously. 



Fig. 221. Typical Spring Collets 


156 






































MACHINE SHOP WORK 


145 


TYPES OF MILLING MACHINES 

Bench Miller. In taking up the subject of machines devoted 
especially to milling, it is well to consider that the transition from 



Fig. 222. Rivett Lathe with Milling Attachment 
Courtesy of Rivett Lathe Manufacturing Company, Boston, Massachusetts 

milling in the lathe to 
the special milling ma¬ 
chine was bridged by an 
attachment to the lathe 
by which the functions 
of the milling machine 
are well served. This is 
especially noticeable in 
the milling attachment 
attached to bench lathes, 

Fig. 222, said attach¬ 
ment being mounted on 
the bed of the lathe and 
the spindle provided 

with a milling cutter. Fig 223 BenchMilIer 

This arrangement is 

used for simple milling operations. Such devices led to the intro¬ 
duction of the bench miller, Fig. 223, which is naturally intended for 
small work only, and therefore is not provided with automatic feeds, 
hand-feeding by means of levers being used. 



157 











146 


MACHINE SHOP WORK 


Horizontal Milling Machine. The horizontal milling machine, 
Fig. 224, consists of a frame or box structure carrying a horizontal 
spindle in the upper portion, together with brackets or an over¬ 
hanging arm to steady the spindle. The front of the frame is care¬ 
fully machined and hand-scraped at right angles to the spindle; and 
there is mounted on the front a knee, the upper surface of which is 
parallel to the spindle in the horizontal plane and capable of move- 



Fig. 224. Horizontal Milling Machine—Column Type 
Courtesy of Brown and Sharpe Manufacturing Company , Providence, Rhode island 


ment in a vertical direction. This knee carries what is known as the 
saddle, the upper portion of which is also parallel to the spindle. 
The movement of the saddle is toward and from the frame of the 
machine, and therefore parallel to the spindle. The saddle, in turn, 
carries the table, to which the work is attached by means that will 
be described. The upper surface of the table is parallel to the spindle, 
and the table movement is at right angles to the spindle in the 
horizontal plane. 


158 







MACHINE SHOP WORK 


147 


The combination of these three motions at right angles to the 
spindle in the vertical plane, parallel to the spindle in the horizontal 
plane, and at right angles to the spindle in the horizontal plane, gives 
to the milling machine what is known as its range. It allows any 
portion of the table to be brought under the cutter at any distance 
covered by the vertical feed. 

Micrometer Graduations. It will be seen, therefore, that one of 
the principal advantages of the milling machine is its wide range 



Fig. 225. Slabbing Miller—Planer Type 
Courtesy of Ingersoll Milling Machine Company, Rockford, Illinois 

of working capacity, and the accuracy with which the table can be 
placed with relation to the cutter. This accuracy is obtained by means 
of graduated dials on the feed-screws, which are read directly to 
.001 inch, and, by estimation, to .00025 inch. For many years the 
milling machine was the only tool which supplied these micrometer 
graduations, but they are now applied to nearly every class of machine 
tool in which accurate adjustment is necessary. A common method 
of graduation is by the use of a screw with a pitch of | inch 


159 







148 


MACHINE SHOP WORK 


and with 200 graduations on its dial. In some cases, a screw with 
a pitch of \ inch is used with 250 graduations, but it is always safe 
to assume that the single graduation on a milling machine means a 
movement of .001 inch 

Avoiding Backlash Error. Lost motion or backlash between the 
screw and its nut, in any of these adjustments, is a cause of frequent 
error, and should always be considered. Even for a machine in 



Fig. 226. Planer Type Four-Spindle Milling Machine 
Courtesy of Ingei'soll Milling Machine Company, Rockford, Illinois 

excellent condition, when the motion of the screw is reversed, the 
screw will turn through an angle giving the equivalent of about 
.005 inch movement of the part being fed along, but with no actual 
movement of the part. As an example, if, in moving the table from 
the column, the operator carries it .003 inch too far, it will not suffice 
simply to turn the dial back three graduations. The table should be 
brought back several hundredths of an inch, and again advanced to 
within .003 inch of its former position. In order to facilitate the 


160 





MACHINE SHOP WORK 


149 


quick and accurate reading of these dials, they are arranged so that 
they can be readily set to zero whenever desired. 

Distinction between Plain and Universal Millers. The move¬ 
ments above described for the adjustment of the work are those 
necessary for what is termed a plain milling machine. In order to 



have a universal milling machine, Fig. 224, it is necessary that the 
table be so arranged that it can be swung upon the saddle in the 
horizontal plane, so that its feeding movement is not at right angles 
to the axis of the spindle. Universal milling machines usually have 


161 














150 


MACHINE SHOP WORK 


a total working angular movement of 90 degrees, 45 degrees on 
either side of the normal position. 

While the milling machine developed from the lathe, through the 
Lincoln miller, to the standard horizontal universal machine, its 
development for work on which heavy cuts are necessary took an 
opposite course. 

Planer Type Milling Machines. The slabbing miller, Fig. 225, 
is of the planer type, the cross-rail carrying a rigidly supported cutter, 
while the table has the comparatively slow feed required for milling. 
This type of machine is especially valuable where broad surfaces are 
to be machined on pieces of work which are of such shape that they 
can be readily and uniformly supported to withstand the cut. 

Another milling machine of 
the planer type, having 
four spindles, is shown in 
Fig. 226. It is designed for 
very heavy work. 

Especial Care Neces¬ 
sary to Keep Work True. In 
order to produce true w T ork 
by heavy milling, it is not 
only necessary that the 
work shall be supported as 
already outlined, but also 
that the cut be nearly uni¬ 
form in depth and width. 
If the section of the cut varies greatly, or, even with uniform cut, if 
the work is irregularly supported, the metal will spring under the 
influence of the cutter, and it will be found that the work is not 
true. Therefore, work of a character that from its shape is especially 
liable to be distorted by the process of milling, may be machined to 
better advantage by the process of planing. 

Milling Attachments for Planer. It is often desirable, from the 
point of view of economy of time, to combine the operations of milling 
and planing,, and, with this end in view, milling attachments are made 
for the planer in a single machine, Fig. 227, and attached to the cross¬ 
rail. The changes required from the planer drive, are an extra belt 
to rotate the cutter, and a special countershaft to slow down the move- 



1G2 








MACHINE SHOP WORK 


151 


ment of the table. This attachment can carry a slabbing, gang, or 
formed cutter on an arbor for horizontal milling; or it can carry end 
mills, Fig. 228, by turning the attached head through 90 degrees, 
thus bringing the spindle to a vertical position. This last arrange¬ 
ment of the spindle is of great utility, as it allows cutters to reach 
down into places w T hich would be inaccessible by any other means. 

Vertical Milling Machines. Vertical Head on Horizontal 
Machines . The advantages of the vertical milling spindle are so 



Fig. 229. Vertical Milling Hoad Attached to Horizontal Milling Machine 
Courtesy of Brown and Sharpe Manufacturing Company, 
Providence, Rhode Island 


evident that nearly all makers of horizontal machines furnish what is 
called a vertical head, Fig. 229. This vertical head is very rigidly 
supported on the column by means of the overhanging arm, so 
that cuts can be taken of as great depth as with the horizontal 
spindle. The vertical spindle can also be turned in the vertical plane, 
so that an end mill can be used at any angle with the table. 

Vertical Spindles Only. There are several machines made in 
which the vertical spindle alone is employed, Fig. 230, there being 
no provision for a horizontal spindle. 


1G3 







152 MACHINE SHOP WORK 

Such machines are provided with the feed motions of the 
horizontal type, and also with a rotating table by which circular 
work can be done. A large amount of work formerly done in lathes 


Fig. 230. Vertical Milling Machine with Working Parts Shown in Ghost 
Courtesy of Becker Milling Machine Company, Hyde Park, Massachusetts 

is now being done in vertical spindle machines, as well as many 
pieces formerly machined on planers and shapers. 

Duplex Milling Machines. The duplex milling machine, 
Eig. 231, has both the horizontal and vertical spindles combined in 
one, which allows the spindle to be placed at any angle from horizontal 
to vertical, and combines all the good points of both machines. The 


164 










MACHINE SHOP WORK 153 

head of the duplex miller can be moved out over the table so as greatly 
to increase the range of the machine; and this head is also provided 
with a drilling attachment whereby holes may be drilled at any angle. 


Fig. 231. Duplex Milling Machine Set for Cutting Spirals 
Courtesy of Van Norman Machine Tool Company, Springfield, Massachusetts 

milling operations 

Classification. These may be classified in a manner similar to 
the cutters themselves, whose names will suggest the kind of work for 
which they are adapted. 

Plane Milling or Surface Milling. This is the machining ot 
plain, flat, horizontal surfaces by means of cylindrical mills whose 
length is usually much greater than their diameters, the larger kinds 
being constructed with inserted blades or teeth. . 

Side Milling or Face Milling. This operation is the machining 
of vertical surfaces, or surfaces at right angles to the axis of the 
milling cutter. 


165 


154 


MACHINE SHOP WORK 


Angle Milling. As the name suggests, this is the machining of a 
surface at some other than a right angle to the axis of the milling cutter. 

Form Milling . The machining of some special cross-section 
generally composed of straight lines and curves, or wholly of curves, 
is called form milling. 

Profiling. This operation is usually considered as machining 
the vertical edges of pieces of irregular contour, and is generally done 
with an end mill mounted in a vertical spindle. The exact form is 
generally determined by a templet or profile attached to the piece 
or to the fixture supporting it. 

Care of Milling Cutters. This is a matter of much importance, 
since a worn or dull cutter will never produce good work, and a good 
cutter is soon spoiled by improper use or lack of care in handling. 
The cutting edge should always be sharp and keen; but it is of still 
greater importance that each edge should be exactly the same distance 
from the axis of rotation—or, in other words, that the cutters should 
run true. When this condition does not exist, the greater part of the 
work will fall upon two or three of the teeth, and these will be 
speedily ruined, while the others do little or no work. 

Care should be taken to have the arbor run true; otherwise a 
cutter that is ground true will not run so. Therefore, cutter arbors 
should be examined and tested frequently to see that the portion 
upon which the cutter or loose collars rest runs true and is smooth, 
and not defaced by bruises from rough handling. 

Grinding Milling Cutters. A good cutter-grinding machine is 
absolutely essential. It should have a well fitted and true spindle, 
and such attachments for holding cutters of various kinds as to be 
able to grind all the usual forms without important changes of 
mechanism. The centers for supporting arbors, and the devices for 
holding cutters not on arbors, should be well fitted and true. The 
machine should be equipped with such graduated circles as will 
enable the operator readily to set it for grinding all the usually 
required angles. 

Fig. 232 shows a regular machine for this purpose. It is so 
arranged that various forms of cutters can be ground either when 
mounted upon cutter arbors or held in the machine fixture provided; 
and it has a number of well-designed attachments by which a con¬ 
siderable amount of general grinding can be successfully done. 


166 


MACHINE SHOP WORK 


155 



In keeping milling cutters in order, they should be ground as 
soon as they become dulled, whether wanted for immediate use or 
not. It is more economical to have them always ready, as the 
emergency is likely to occur at a time when a cutter is wanted at 
once, and when there is not time to grind it properly. 

Cutters should be kept sharp. A dull cutter will not only wear 
away more rapidly than a sharp one, but it will also do poor work; 


Fig. 232. “Cincinnati” No. 2 Universal Cutter and Tool Grinder 
Courtesy of Cincinnati Milling Machine Company, Cincinnati, Ohio 

it will take a great deal more power to drive it, and the milling 
machine will be more rapidly w r orn out. 

Care should be taken, in grinding angular cutters, that the 
points are not heated so as to draw the temper. This very easily 
happens if considerable care is not used, the cutting edges becoming 
so softened as to be rapidly w^orn away and the cutter spoiled by use. 
Formed cutters are frequently affected in a similar manner. The 
excessive friction of a dull cutter will frequently generate a sufficient 
amount of heat to draw the temper of the teeth at the cutting edge. 


167 





156 


MACHINE SHOP WORK 


In making the grinding machine ready to grind a cutter, it is 
necessary to see that the emery wheel runs perfectly true; and if it 
does not, it should be trued up before any grinding work is done. 
If the cutter is to be mounted upon an arbor, the latter should be 
tested to ascertain if it runs true before putting the cutter on it. 
In grinding the cutter, light grinding cuts should be taken, and the 
cutter moved rapidly across the face of the wheel. The wheel should 
be the proper grade of emery, not finer than 90, nor coarser than 56. 
The coarser and softer the wheel, the higher may be the speed. It is 
not advisable to make the speed over 4,500 feet per minute at the 
outer edge of the wheel. The cutting edge of the wheel need not be 
over an eighth of an inch thick, in any case. 

Preparing the Milling Machine for Work. The taper shank 
of the arbor and the hole in the spindle should be wiped clean and 
free from oil or grit. Should the outer end of the arbor be sup¬ 
ported by a pointed center or a bushing, it will not be difficult to 
keep it in place; but if not so supported, it must be driven tightly into 
the spindle, using care that the flattened end or tang fits perfectly 
into the slot provided for it. If it is noticed that the arbor does not 
fit fairly into the spindle, it should be removed and examined to see 
that there are no dents or bruises on it, and that the tang is not too 
long or too thick, or the shoulders not cut back far enough to permit 
it to fit properly. When arbors work loose, it is on account of some 
one of these causes. 

If the arbor does not run true when the cutter is mounted and 
the clamp-nut screwed up, the nut and collars should be removed 
and examined. Fine chips or dirt are likely to be found between 
the collars, or between them and the cutter, causing the arbor to 
spring when the clamp nut is screwed up. The parts should be 
cleaned and again put in place. 

Cutting Speeds. Conditions Governing Speed. There are no 
hard and fast rules that will properly govern a majority of cases of 
the continually varying conditions of milling cutters, machines, and 
the material to be machined. In any case, much must be left to the 
judgment of the foreman and the operator. Prominent among the 
conditions that tend to vary the cutting speed are the following: 

The cutter may be newly ground, keen, and sharp; or it may have been 
considerably dulled by use. While not dull enough to require grinding, it will 


168 


MACHINE SHOP WORK 


157 


not be safe to run it up to the speed of a sharp cutter. The teeth may be worn 
thin from long use and re-grinding, and not strong enough to stand the strain 
of maximum speed. The cutter may be of such a form—as a double-angle 
cutter—that the teeth will not bear the strain of full speed. 

The machine may be well designed and built, and free from vibration; or 
it may be directly the reverse, a fast speed producing so much chattering as to 
spoil both work and cutter. The arbor may be large and stiff, or small and 
slender. In one case, a. fast speed may be maintained; and in the other, both 
work and cutter would suffer. The driving gearing may be well designed and 
its teeth fit accurately with no backlash; or it may be poorly designed and 
made, or much worn, and cause much chattering on a fast speed. There are 
many other similar conditions. 

The material may be of varying degrees of hardness and toughness, and of a 
great variety of forms. Some iron castings will be more severe on a cutter 
than tool steel would be. The scale on cast metal is very hard to cut through, 
and dulls the teeth of a cutter quickly. The varying hardness of steel, from 
that ordinarily found in the bar to that properly annealed, is great. The amount 
of carbon in steel is always a varying condition for which it is difficult to formu¬ 
late rules. Therefore it is only possible to give rules that will meet a fair average 
of conditions. 

In order to accommodate different sizes of cutters, maintain a 
uniform cutting speed, and also allow for difference in hardness of 
the material being worked, it is necessary that the milling machine 
should be supplied with several speeds. In the ordinary miller we 
usually have a four-step cone with back gears, which gives eight 
speeds with a single overhead belt. The countershafts for these 
machines are of the friction type, and are supplied with two driving 
pulleys driving in the same direction, but at different speeds, giving a 
total, including the back gears, of sixteen speeds for each machine. 

Form of Cutter as Affecting Its Speed and Feed. A slitting cutter 
(practically a saw) may be run much faster than one of broad face. 

A cutter of small diameter will cut faster than a large one, as 
the arc of action is much less. 

Angle cutters must be run at lower relative speeds so as not to 
break off the slender points of the teeth. 

The speed may sometimes be profitably increased without 
changing the rate of feed. Again, the speed should be decreased 
according to the conditions of the work. 

There is no direct and constant ratio between speed and feed. 
Conditions may vary either one without changing the other. 

A roughing cut will often work better with a moderate speed and 
a coarse feed. The smoothness of the work is not so important as 


169 


158 


MACHINE SHOP WORK 


taking off the surplus stock. With a finishing cut, the conditions 
are reversed and a fine feed is necessary. 

Cutters with inserted blades will not usually stand as high a 
speed as solid cutters, particularly w r hen the blades have a large 
cutting surface. This condition is emphasized when cutting rather 
hard and tough material. 

If there is a comparatively small space for chips between the 
teeth of the cutter, a light cut must be taken, or slower speed used, 
so that the chips will not clog the cutter. 

Speed Used on Particular Work or 
Material. The speed used on any par¬ 
ticular work depends, as before stated, 
on the diameter of the cutter and the 
character of the work. Thus, with car¬ 
bon steel cutters, the cutting speed will 
be 30 to 60 feet per minute. With high¬ 
speed steel cutters, double these speeds 
may be maintained if the drive of the 
machine is strong enough to pull the cut. 

When using very small cutters, the 
machine itself will not usually give a 
speed which is high enough to suit the 
diameter of the cutter. For such work, 
a high-speed attachment, Fig. 233, is 
furnished, by which the small, light 
cutters may be driven at a suitable rate. 

Of equal importance with the correct speed for the cutter, is the 
maximum feed or table speed, which is reckoned in inches per minute. 
A more logical method of designating the feeds, and one which has 
been adopted by several makers, is to give the advance of the table 
in thousandths of an inch for every turn of the spindle. 

Based upon the use of the ordinary carbon steel cutters, the 
Brown and Sharpe Manufacturing Company have prepared the 
following statements regarding the speed of mills: 



. 233. High-Speed Attachment 
for Milling Machine 


It is impossible to give definite rules for the speed and feed of mills. The 
judgment of the foreman or man in charge of the machine should determine 
what is best in each instance. 

As usually the highest possible speed and feed are desirable, it pays to 
increase them both until it is seen that something will break or burn, and then 


170 






MACHINE SHOP WORK 


159 


TABLE IV 

Speeds and Feeds for Milling Cutters* 


Material 

Speed 

(ft. per min.) 

Feed 

(in. per min.) 

Soft cast iron 

60 

u 

Hard cast steel 

40 

1 

Wrought iron 

45 

1 

Soft machine steel 

36 

\ 

Hard machine steel 

24 

2 

Tool steel, annealed 

30 

1 

2 

Tool steel, not annealed 

20 

I 

4 

Soft brass 

120 

21 

Hard brass 

100 

21 

Bronze 

80 

1| 

Bronze, gun metal 

60 

1 

Vulcanized fiber (gray and red) 

60 

6 


reduce to a speed and feed of safety. Sometimes the speed must be reduced, 
and yet the feed need not be changed. 

The average speed on wrought iron and annealed steel, using carbon steel 
cutters, is perhaps 40 feet per minute, which gives about sixty turns per minute 
with mills 2| inches in diameter. The feed of the work for this surface speed 
of the mill can be about l£ inches per minute, and the depth of the cut about 
^ inch. In cast iron, a mill can have a surface speed of about 50 feet a minute 
while the feed is 1| inches per minute and the cut ts inch deep. In tough brass, 
the speed may be 80 feet, the feed the same as in cast iron, and the chip & inch. 

As small mills cut faster than large ones, an end mill, for example, \ inch 
in diameter, can be run about 400 revolutions per minute with a feed of 4 inches. 

Addy, an English authority, gives as a safe speed for cutters of 

6 inches diameter and upward: 

Steel, 36 ft. 'per min., with a feed of £ in. per min. 

Wrought iron, 48 ft. per min., with a feed of 1 in. per min. 

Cast iron, 60 ft. per min., with a feed of If in. per min. 

Brass, 120 feet per min., with a feed of 2f in. per min. 

He also gives a simple rule for obtaining the speed: 

The number of revolutions which the cutter should make when working 
on cast iron equals 240 divided by the diameter in inches. 

In Table IV are given the average speeds in feet per minute 
of the periphery of the cutter, and the rate of feed in inches per 
minute for various materials. 

Tables V, VI, VII, and VIII, have been prepared by the 
Brown and Sharpe Manufacturing Company, to give the speed, 
feed, and depth of cut that can be obtained with a machine similar 
to that illustrated in Fig. 224. It is understood that these speeds 

‘Attention is called to the seemingly slow speed and fast feed for vulcanized fiber. 
Practice, however, proves it to be correct. 


171 







160 


MACHINE SHOP WORK 


TABLE V 


Surface Milling of Cast Iron 




Speed of 



Feed per Minute 

Diameter 

Revolutions 
per Minute 

Depth of 

Width of 



of Mill 
( in.) 

Cutter 
per Minute 
( ft.) 

Cut 

(in.) 

Cut 

(in.) 

In Scale 
of Cast 

Under 
Scale of 


Iron 

Cast Iron 






(in.) 

(in.) 


42 

34 

i 

1 6 

1 

6f 

81 


42 

34 

1 

2 

1 

41 

61 

Q 

42 

34 

1 

16 

2 

6f 

81 

o 

42 

34 

1 

2 

' 2 

21 

41 


42 

34 

1 

1 6 

3 

6f 

81 


42 

34 

7 

16 

3 

1 a 

1 8 

2A 

*3 1 

42 

40 

S 

32 

8 

41 

64 

o 2 

42 

40 

1 

8 

31 

21 

31 


42 

50 

1 

2 

4* 

61 


42 

50 

1 

4 

31 

41 

4-i 

42 

50 

1 

6 

2 

21 


42 

50 

i 

8 

6 

41 

8 

61 


42 

50 

11 

32 

12 

1 8 

2 


TABLE VI 

Surface Milling of Soft Machinery Steel 


Diameter 
of Mill 
( in.) 

Revolutions 
per Minute 

Speed of 
Cutter 
per Minute 
( ft.) 

Depth of 
Cut 
( in.) 

Width of 
Cut 
( in.) 

Feed pep 

In Scale 
of S.M.S. 
(in.) 

Minute 

Under 
Scale of 
S.M.S. 

(in.) 


38 

30 

1 

16 

1 

6 

8 


38 

30 

1 

0 

1 

11 

11 

Q 

38 

30 

I 

16 

*2 

9 3 
" 8 

31 

O 

38 

30 

1 

2 

2 

3 

4 

H 


38 

30 

1 

16 

3 

11 

17 

1 8 


38 

30 

3 

8 

3 

3 

4 

H 

QI 

38 

35 

1 

16 

8 

1 * 

1 8 

3 

°2 

38 

35 

1 

8 

8 

3 

4 

n 


25 

30 

1 

16 

3 

4 

5 


25 

30 

1 

1 6 

5 

2 1 

41 

41 
■* 2 

25 

30 

3 

8 

5 


1 

2 


25 

30 

1 

1 6 

10 

n 

2 1 


25 

30 

3 

16 

10 

1 

2 

7 

8 


and feeds are those used when the milling cutters are made from a 
good grade of carbon tool steel. If the cutters used are made from 
the newer high-speed steels, these figures can be decidedly increased. 


172 




























MACHINE SHOP WORK 161 


TABLE VII 

End or Face Milling of Cast Iron 







Feed per Minute 

Diameter 
of Mill 
( in.) 


Speed of 

Depth of 




Revolutions 

Cutter 

Width of 



i er Minute 

per Minute 

Cut 

Cut 

In Scale 

Under 


(ft.) 

(in.) 

(in.) 

of Cast 

Scale of 





Iron 

Cast Iron 






(in.) 

(in.) 

1 

382 

50 

l 

16 

1 

2 

23 

35 

2 

382 

50' 

1 

8 

1 

2 

7 

11 

1 

191 

50 

i 

16 

1 

30 

40 

191 

50 

1 

2 

l 

3 


1 4 

109 

50 

1 

8 

1 & 

1 4 

17 

23 

109 

50 

3 

4 

11 

1 4 

3| 

41 

8 

5 

42 

55 

1 

4 

5 

21 

41 

16 

10 

45 

1 

4 

16 

7 

8 

1 


TABLE VIII 

Face Milling of Soft Machinery Steel 







Feed per Minute 



Speed of 
Cutter 
per Minute 

(ft.) 





Diameter 
of Mill 
( in.) 

Revolutions 
per Minute 

Depth of 
Cut 
( in.) 

Width of 
Cut 
( in.) 

In Scale 
of S. M. S. 
(in.) 

Under 
Scale of 

S. M S. 
(in.) 

1 

267 

35 

1 

1 6 

1 

2 



2 

267 

35 

1 

4 

1 

2 



1 

152 

40 

1 

16 

1 

3 

41 

152 

40 

1 

2 

1 



1 3 

1 4 

87 

40 

1 

16 

1 4 

91 

"4 

4* 

87 

40 

3 

4 

1 3- 

1 4 


If 


Use of Oil on Machines and Work. The milling machine, and 
in fact all the machines of the shop can do efficient work only when 
they are well cared for. An important element is that they should 
be frequently cleaned and well oiled. 

Great care should be exercised that chips do not get into the 
tapered holes in the spindles or between the arbor collars. 

When at work on steel, the milling cutter is kept flooded with 
oil or a solution of sal soda, as already specified for lathe work. 


173 






































162 


MACHINE SHOP WORK 


Oil is used in milling to obtain smoother work, to make the 
mills last longer, and, where the nature of the work requires, to wash 
the chips from the work or from the teeth of the cutters. Some 
lubricant is generally used in milling steel, wrought iron, malleable 
iron, or tough bronze. Frequently, when only a few pieces are to 
be milled, it is not used, and some steel castings are milled without a 
lubricant; also in cutting cast iron it is not used. For light, flat cuts 
it is often put on with a brush, giving the work a thin covering like 
a varnish. For heavy cuts it should be led to the mill from the drip 
can that is usually sent with each machine; or it should be pumped 
upon or across the mill when cutting deep grooves, milling several 
grooves at one time, or, indeed, in milling any work where, if the 
chips should stick, they might catch between the teeth and sides of 
the grooves, and scratch or bend the work. 

The Brown and Sharpe Manufacturing Company recommend the 
use of lard oil in milling. Any animal or fish oil, however, may be 
used, and then separated from the chips by the use of a centrifugal 
separator or by dumping into a tank of water. In the latter method, 
the chips fall to the bottom and the oil rises to the top, whence it may 
be drawn off with but little waste. 

Laying Out and Drilling Holes. One of the operations for which 
the miller is particularly adapted is in locating and drilling holes 

which require accurate placing. 
The graduated feeds of the mill¬ 
ing machine allow the distances 
to be set off as closely as .00025 
inch, and holes can also be drilled 
to a given depth with equal accu¬ 
racy. In starting holes, it is best 
to use a spotting drill, Fig. 234, 
Fig. 234. spotting Drill which is extremely rigid and per¬ 

fectly true. The spot made should be of slightly greater diameter 
than the drill to be used. The drill should be what is known as 
reamer size—that is, & inch below the standard—and the hole may 
then be reamed, either in one operation, using a standard reamer, or 
by first using a machine reamer which is about .005 inch under size, 
to be followed by the standard reamer. It is evident that holes 
thus drilled and reamed will be parallel, and, by using the vertical 



174 





















MACHINE SHOP WORK 


163 


head, holes can be drilled at right angles in like manner. When 
extreme accuracy in holes is demanded, a boring bar may be used in 
the spindle after the drill, 
in order to correct any error 
due to the running of the 
drill itself. 

Splining Shafts. An¬ 
other operation suited to the 
milling machine, although 
sometimes performed on the 
shaper or planer, is that of 
splining shafts. The slots 
in the table give the proper 
alignment to the shaft; the 
cutter can be set with cor¬ 
rect relation to the axis 
without difficulty, and the 
spline cut full depth at one 

operation. The only objec- Fig - 235> Splining^Arrangement with End Mill 
tion to this form of spline is 
the curve at the end due to 
the shape of the cutter. An 
end mill in the vertical head 
can be used to remove this 
objectionable feature; and 
some splining machines are 
made. Fig. 235, which per¬ 
manently carry both cut¬ 
ters, so that the work can 
be quickly shifted from one 
to the other. 

Making Dovetails. The 
operation of making dove¬ 
tails, which is a delicate and 
expensive job on a shaper, 

23 readily performed on the Fig. 236. Dovetail Cutter on Vertical Milling Machine 

milling machine, especially of the vertical type, Fig. 236, the cutter 
being a form of end mill suited to the size and angle of the dovetail. 




175 











164 


MACHINE SHOP WORK 



Fig. 237. Fluting Taper Reamer 
Courtesy of Van Norman Machine Tool Company, 
Springfield, Massachusetts 


T-slots are cut in a similar manner, either directly from the solid, 
or by following a groove made with a plain cutter. 

Fluting Taps and 
Reamers. One of the 
common operations per¬ 
formed between centers is 
the fluting of taps and 
reamers, Fig. 237, which 
is done by the special 
cutters already referred 
to in Fig. 214. It wflll be 
noticed that the cutter 
should be set in such a 
way that the cutting edge 
of the tap or reamer will 
be radial. If left as an 
obtuse angle, the tool will 
simply scrape and not cut; while, if the tooth is undercut to any 
extent to correct this, it will often be so weakened as to be liable 

to break. 

The flutes in twist drills 
and in spiral fluted reamers 
may also be cut between 
centers; but, if the cutter is 
carried directly by the spin¬ 
dle, the operation requires a 
universal machine. If the 
cutter be carried by a vertical 
or sub-head of any kind, a 
plain machine will answer for 
the purpose. The angle to 
which the table or vertical 
head must be set for spiral 
cutting, Figs. 238 and 239, 
, , is the angle between the axis 

Fig. 23S. Milling Spirals with Table at Angle 0 

and the development of the 
spiral. This angle can be closely determined by the following 
graphical method: 



176 


























MACHINE SHOP WORK 


165 


Construct a right-angled triangle having a base equal to the axial distance 
represented by one full turn of the spiral (this is the lead of the spiral), and a 
perpendicular equal to the circumference of the work, Fig. 240. Draw the 
hypothenuse of this triangle. If the construction has been carefully done, the 



Fig. 239. Cutting Spiral with Milling Machine 
Courtesy of Brown and Sharpe Manufacturing Company, 

Providence, Rhode Island 

angle between the base and the hypothenuse may be closely determined by the 
use of a protractor, and will be the angle to which the table or head must be set. 

This angle can be more closely and quickly determined by a 
very simple problem in plane trigonometry—namely, finding the 
tangent of the angle. To do this, divide the perpendicular of this 
triangle by its base, and obtain the value of the angle from a table 

of tangents. . 

Spirals. The cutting of spirals requires another operation which 

differs from ordinary work. In addition to the angular setting, the 


of Work 


Fig. 240. Graphical Method of Determining Angle for Cutting Spirals 

work must be rotated in order to produce the spiral, as well as fed 
forward to the cutter. This rotation of the work must be positive, 
which means geared; and one rotation of the work will, of course, 



177 












166 MACHINE SHOP WORK 

equal the lead of the spiral, which is usually expressed as one turn in 
n inches. After cutting one spiral groove, the work is turned and 
indexed the same as in plain milling. 

Cams. Both open and closed cams can be readily cut on a plain 
milling machine by the use of the cam-cutting attachment, Fig. 241, 
which nearly all makers are able to furnish. The outline of the cam 
is first laid out and worked down by hand on a plain disc, or male 
leader, as it is termed. This leader and a suitable blank are mounted, 



Fig. 241. Cam-Cutting Attachment for Milling Machine 
Courtesy of Brown and Sharpe Manufacturing Company, 

Providence, Rhode Island 

with their outlines coinciding, on the spindle of the cam-cutting 
attachment. A cam roll of the size to be used is mounted on a 
stationary roll stud; and an end mill of the same diameter, or enough 
larger for clearance, is mounted in the milling machine spindle 
directly opposite the cam roll. The spindle of the cam-cutting 
attachment is mounted on a carriage, which, by means of a weight 
over a pulley at the end of the milling machine table, is always kept 
with the leader in contact with the cam roll. A worm and worm gear 
are used for rotating the attachment, and thus the spindle approaches 


178 



MACHINE SHOP WORK 


167 



or recedes from the cam roll according to the shape of the leader. 
When cutting closed cams, it is sometimes desirable to use the hand¬ 
made male leader as a form from which to make a closed or female 
leader. This female leader will surround the cam roll in such a way 


Fig. 242. Cutting Spur Gear on Milling Machine 
Courtesy of Brown and Sharpe Manufacturing Company, Providence, Rhode Island 

that, even if the weight should fail to act, no serious damage can be 
done to the blank. The cutting of face cams differs from the above 
method only in that the spindle of the attachment is at right angles 
to the spindle of the milling machine, instead of parallel to it. The 
leader and cam roll are used in the same manner as before. 


179 












1G8 


MACHINE SHOP WORK 


Gears. The cutting of gears of all descriptions was formerly 
done on some type of milling machine, although now each type of 
gear may have its special and, in many cases, automatic machine. 



Forms of Cutters. The cutters for milling spur and bevel gears 
are of two types, producing both the cycloidal and the involute tooth. 
For each pitch, the cycloidal system requires twenty-four cutters, 
while eight cutters usually suffice for the involute system. These 
cutters are plainly marked with the style 
of tooth, pitch, and number of teeth for 
which they are suitable. Some cutters 
are also marked with the full depth of the 
tooth expressed in thousandths of an 
inch, Fig. 242. The gear blanks, having 
been very carefully turned as to outside 
diameter, are mounted on an arbor be¬ 
tween centers, and the cutter placed so 
that its central plane passes through, and 
is parallel to, the axis of the arbor. 
Clamp the saddle in this position; raise 
the table knee until the cutter, when 
rotating, just touches the outside of the 
blank. Using the table screw, move from 
under the cutter; using the graduated dial, raise the knee an amount 
equal to the whole depth of the gear tooth. With the exception of 
the indexing, the gear blank is now ready to be cut, Fig. 242. 



180 




















MACHINE SHOP WORK 


169 


Use of Dividing Head. In order that the gear may be accurately 
and quickly set for cutting each tooth, a dividing head is used, which 
is shown in Fig. 243. The mandrel upon which the gear blank is 
mounted is held by the centers A A, and firmly dogged to the face¬ 
plate B. The index plate C is geared to the head spindle that carries 



Fig. 245. Hobbing Teeth in Worm Wheel 
Courtesy of Brown and Sharpe Manufacturing Company, Providence, Rhode Island 

the faceplate B; the index plate is provided with a number of holes. 
These holes are arranged in circles, each circle having a different 
number of holes, and these holes are accurately spaced at equal 
distances apart. The arm D carries a stem E, having a knurled head 
at one end and a pin at the other. The pin is held in one of the holes 


181 







170 


MACHINE SHOP WORK 





of the index plate by a spring. The arm D can be moved to any 
desired position relative to the index plate, and there fastened. 

When a gear is to be cut, the arm D is shifted so that the pin is 
opposite a row of holes the number of which is the same as the 
number of teeth to be cut, or a multiple of that number. Thus, 


Fig. 246. Rack-Cutting Attachment on Milling Machine 
Courtesy of Brown and Sharpe Manufacturing Company, Providence, Rhode Island 

suppose a gear with 45 teeth is to be made. The pin may be set 
opposite the circle of 90 holes. Assuming that the ratio of revolution 
between D and B is 40 to 1; xV of a revolution at B requires ft of a 
revolution at D. The pin E must, therefore, be moved xx of 90 holes, 
or 80 holes, for each tooth cut. 


182 





MACHINE SHOP WORK 


171 


Bevel Gears. Bevel gears are held on a taper-shank arbor in the 
dividing head, which is swung up to bring the bottom of the tooth 
parallel with the table, Fig. 244. As all parts of the tooth of a bevel 
gear are elements of a cone, it is evident that both the tooth and the 
space should vanish at the apex of the cone. No solid cutter, there¬ 
fore, can do more than give an approximately correct shape to the 
tooth; for this reason two cuts are made in order more nearly to 
approach the desired contour. 

Spiral Gears. Spiral gears are cut in the same manner as any 
other spiral—that is, by using the angular setting of the head or 
table with positive rotation of the work. 

Worm Gears. Worm gears can be hobbed out by two different 
methods. A common method is to gash the blank with a stocking 
cutter; then mount it on an arbor held freely between centers, so 
that the hob, w T hen sunk in the gashes, will rotate the blank. The 
blank is raised slowly against the rotating hob until the hob reaches 
the proper tooth depth. A more accurate method is by means of a 
train of gearing to rotate the blank positively at a speed corresponding 
to the pitch of the hob, and raise the rotating blank against the 
rotating hob until the proper tooth depth is obtained. This method 
requires no preliminary gashing, Fig. 245. 

Rack Cutting. Rack cutting requires a special attachment, 
Fig. 246, so that the cutter spindle may be carried at right angles 
to the length of the table. 

GRINDING MACHINE 

Value of Grinding as Finishing Process. When greater accuracy 
than that obtainable on the milling machine or the lathe is required, 
recourse is had to grinding. This operation depends upon the abrasive 
or cutting qualities of emery, corundum, and carborundum. With 
work properly held to a solid grinding wheel, it is not difficult to 
attain great accuracy. By means of the grinding machine, parts 
may be economically finished, even in hardened steel that could 
not possibly be machined on such shop tools as the lathe, planer, 
or shaper. One type of machine used for this purpose is shown 
in Fig. 247. With such a machine, round surfaces may be 
ground so that the variation from the nominal diameter is less 
than .0001 inch. 


183 


172 


MACHINE SHOP WORK 


Features of Grinding Process. The grinding machine illustrated 
in Fig. 247 consists of a strong base A , upon which there is mounted 
a headstock B and a tailstock C, similar in action to those of an 
ordinary lathe. Back of these is an emery wheel driven by a separate 
belt. The principle of operation for round surfaces, is that the part 
to be ground is put upon the centers, and driven exactly as in the 
ordinary lathe. The only additional precaution to be taken is that 



Fig. 247. Cylindrical-Grinding Machine 


the driving apparatus should be secure, so that none of the parts are 
loose. This insures a continuous motion for the piece with no 
possibility of backlash. The piece runs toward the operator, and 
the emery wheel runs in the same direction. The two surfaces of 
wheel and work in contact are therefore moving in opposite directions. 

The headstock and tailstock are mounted upon a traveling table 
D, which moves back and forth in the same manner as the platen 
of a planer. It is made to stop automatically at each end of the stroke. 


184 








































MACHINE SHOP WORK 


173 


When work is being done, the piece is centered, w r ith its axis 
parallel to the line of travel of the table. With the piece and emery 
wheel in motion, the former travels to and fro in front of the lathe. 
The wheel is then gradually moved forward until it has ground the 
work down to the size required. 

It is not intended that large amounts of metal shall be removed 
by this machine. Its object is to reduce to accurate dimensions the 
w ork that has already been turned in the lathe. The proper method 
to pursue is to turn the piece to as nearly the required diameter as 
possible in the lathe, care being taken that it is left a trifle large. This 
may be .01 inch on each 2 inches of diameter. The surplus metal may 
then be removed by grinding. In the machine illustrated in Fig. 247, 
the transverse movement of the wKeel-stand is adjusted by a hand- 
wheel graduated to read to .001 inch on the diameter of the work. 
The machine is also provided wflth an automatic cross-feed, which 
gives a range of advance of the wdieel varying from .00025 inch to 
.004 inch at each reversal of the table. This feed, furthermore, is 
so arranged that it can be automatically released at any point. 

Finishing to Size after Casehardening. This method of finish¬ 
ing is also used for pieces that have been casehardened. Case- 
hardening always w^arps the metal to wFich it is applied. Grinding 
is resorted to in order to reduce it to the proper shape. An example 
of this may be taken in the method used in the manufacturing of 
w T rought-iron locomotive crank pins. The pin is forged and turned 
to as near the working size as possible. It is then casehardened and 
ground to exact alignment and dimensions. 

Grinding is also used for truing work that comes from the lathe. 
The lathe does not turn its w r ork round, ow ing to difference in the 
density of the metal, variation in the cutting speed, dulling of the 
tool, lost motion on the centers and in the spindle, and springing of 
the work itself due to pressure of the tool. The grinding machine 
remedies this to a great extent—partly because only a very slight 
pressure is brought against the w r ork; partly because of the greater 
delicacy of adjustment of the grinding machine as compared with 
the lathe. 

The method of grinding flat surfaces is practically similar to 
that used for round. The work is bolted to the table and moved to 
and fro beneath the emery wheel, w T hich is given a transverse move- 


185 


174 


MACHINE SHOP WORK 


ment so as to cover the whole of the surface to be operated upon. 
The surface speed of the wheel may range from 4,500 to 6,000 feet 
per minute. 

Action of Typical Grinder. Fig. 248 shows a typical surface- 
grinding machine built by the Brown and Sharpe Manufacturing 
Company, which is well adapted to the work of accurately grinding 
flat surfaces up to quite large dimensions. The work table travels 



Fig. 21S. Surface-Grinding Machine 


to and fro in a manner similar to that of a planer, and carries adjust¬ 
able reversing dogs which may be set to limit the extent or position 
of the travel. The grinding wheel mechanism is supported upon a 
cross-rail similar to that in a planer and capable of vertical adjust¬ 
ment on the arc of a circle whose center is the driving shaft supplying 
power to drive the grinding wheel. The wheel mechanism carrying 
the grinding wheel has a transverse, automatic feed the entire width 
of the work table. 


186 







MACHINE SHOP WORK 


175 


In using this machine, the work is clamped directly to the table 
or held in any convenient fixture, as a milling machine or planer chuck 
or vise. In strapping work to the table, it must be rigidly held in 
place; but it is not necessary to clamp it down as tightly as on the 
milling machine or planer table, and great care should be used to 
avoid springing, warping, or other distortion, as grinding work is 
expected to be very true and accurate; in fact, this is its chief claim 
as a method of finishing surfaces. 

To avoid distortion from overheating, comparatively thin wheels 
are generally used, particularly if the piece being ground is thin and 
light, as a thin casting of complicated form. 

Selecting the Grinding Wheel. Grinding wheels are made with 
abrasives as coarse as No. 46, and as fine as No. 150. There is a 
great difference in the degree of hardness of a wheel due to the 
kind of bond, or adhesive material, with which the abrasive is mixed 
in forming the mass of which the wheel is composed. As to the fine¬ 
ness of the abrasive, that as coarse as No. 46 is suited for work on 
rough castings, as in the cleaning room of a foundry. For general 
work in shop grinding, the roughing-off will be best done with a 
wheel of about No. 60; and ordinary finishing, with about No. 90. 
For very fine finishing, the wheel may be much finer. 

As to the degree of hardness of a wheel, it may be generally said 
that the harder the material to be ground the softer should be the 
wheel. There are several degrees of hardness made by the manu¬ 
facturers, the simplest classification being Hard, Medium, and Soft, 
designated by the letters H, M, and S, respectively. All letters stand¬ 
ing before M in the alphabet, refer to wheels harder than medium; 
and all letters after M refer to wheels softer than medium. 

A coarse wheel grinds faster than a fine one, but leaves deep 
scratches in the work. A soft wheel may be made of a much finer 
grade than a hard one. 

A soft wheel grinds faster than a hard one, but it is apt to glaze 
over, or fill up with particles, if used on a soft material. 

Lubrication. To increase the cutting capacity of an abrasive 
wheel, to prevent it from glazing over, and to carry off the heat 
generated by the friction of the wheel on the work, a stream of water 
is frequently used, arrangements being made in most machines— 
particularly in those for grinding tools and for cylindrical grinding— 


187 


176 


MACHINE SHOP WORK 


TABLE IX 

Speed of Grinding Wheels 


Diameter 
of Wheel 
( in.) 

Maximum 
Revolutions 
per Minute 

Diameter 
of Wheel 
( in.) 

Maximum 
Revolutions 
per Minute 

Diameter 
of Wheel 
( in.) 

Maximum 
Revolutions 
per Minute 

1 

19,000 

5 

4,400 

14 

1,580 

u 

12,500 

6 

3,700 

16 

1,380 

2 

19,000 

7 

3,160 

18 

1,230 

2 \ 

8,800 

8 

2,770 

20 

1,100 

3 

7,400 

9 

2,460 

22 

1,000 

3£ 

6,300 

10 

2,210 

24 

920 

4 

5,500 

12 

1,850 

26 

850 


for forcing the stream upon the wheel at the point of contact with the 
work by means of a small pump. For grinding milling cutters, 
reamers, taps, and similar tools, water is not used. 

Table IX gives the maximum speeds of carborundum wheels 
of various diameters. 

The accuracy of grinding renders the use of fine measuring tools 
a necessity. The micrometer caliper, especially with the vernier 
graduation, is best suited for this work. 

While grinding is the only method of finishing some materials, 
such as hardened tool steel, and the most accurate way of finishing 
any kind of stock, its value as an economical method has only lately 
been recognized. The general method of finishing lathe work has 
been to take a roughing cut with about inch feed, then a finishing 
cut with about ylo inch feed, and then file to remove the tool marks. 
In the majority of cases it is more economical, as well as more accu¬ 
rate, to take a roughing cut with J inch feed to within ^ inch of the 
size, and then finish by grinding. 

In some cases it is possible to get excellent results by grinding 
to size directly from the bar without previous turning. 

Lapping. Lapping Holes. Lapping is a term applied to a 
particular method employed in the grinding out of holes. The lap 
consists of a cylinder of soft metal run rapidly inside the hole to be 
lapped, and covered with emery and oil at the same time. The 
surface of the lap should invariably be of soft metal. It may be made 
of copper, or it may be an iron bar with a covering of lead or tin. It 
should be turned slightly tapering at each end, so that it will enter the 
hole. At the middle, it should be a snug fit. 


188 











MACHINE SHOP WORK 


177 


The end of the bar is run through the hole and set on the lathe 
centers with a dog to drive it like an ordinary mandrel. It is covered 
with oil and sprinkled with emery. The lathe is then run at a high 
speed, and the work moved to and fro over the lap. Light pieces 
may be held in the hand. When this is done, care should be taken 
to turn the piece so that the grinding may be even over the whole 
circumference. The tendency, when holding work in the hand, is 
to allow it to rest upon the top of the lap; this causes the grinding to 
be done on one side of the hole unless the piece is frequently turned. 
Laps may be used for 
grinding holes true and 
parallel. For this pur¬ 
pose the work should be 
accurately centered with 
the lap, and firmly bolted 
to the lathe carriage. The 
lap is then run at a 
high speed, and the work 
moved to and fro over it. 

Lapping Flat Sur¬ 
faces. Laps are some¬ 
times used for grinding 
flat surfaces. In such 
cases they are in the 
form of discs. They are 
put on the lathe spindle 
in the place of the face¬ 
plate. The work is then 
pressed against the disc. As the outer edge of the disc has a 
higher speed in feet traveled per minute than those portions nearer 
the center, the grinding is more rapid at the edges. The work must, 
therefore, be constantly turned if it is held in the hand. The best 
way is to clamp it firmly on the lathe carriage, and press it against 
the lap by means of the hand feed. 

Disc Grinder for Flat Top Work. Laps for flat surfaces have 
grown in favor so rapidly that special machines called disc grinders 
have been made to do this work. The construction of the disc grinder 
can be so readily seen from the illustration, Fig. 249, that a detailed 



189 






















178 


MACHINE SHOP WORK 


description is not necessary. For finishing small flat surfaces, espe¬ 
cially those which have been hardened, this machine has become an 
important factor in the modern shop. 

This machine is arranged for using ordinary emery wheels; and 
the grinding is done on the side of the wheel, instead of on its 
periphery; hence its name. The table rest upon which the work is 
held is normally horizontal, but is adapted to be set at any required 
angle when the work is of such a form as to require this adjustment. 

The usual difficulty experienced in. this method of using an 
emery wheel is the liability of the disc to glaze over, and, as a result, 
require frequent turning off to present a good cutting surface. Many 
attempts were made to replace the solid emery wheel with a cast-iron 
disc covered with emery cloth; but the same difficulty was found in 
its use. The experiment was tried, of cutting slight grooves in various 
directions, generally concentric or radial, in the face of the cast-iron 
disc. Its usefulness was improved; but the problem was not solved 
until a single spiral groove was cut, starting near the center and 
running gradually outward. By this means the tendency to glaze is 
broken up in a continually progressive manner that effectually pre- 
vents this trouble. 

Machines similar to the one shown in Fig. 249 are built with 
double heads so that two discs are placed facing each other, one of 
them being capable of adjustment so that flat pieces of work can be 
grooved on both sides simultaneously. Machines of this kind are 
adapted to a considerable range of very useful work. 

LAYING OUT WORK 

Laying out work is one of the most important details of machine 
shop practice. Ordinarily all work is laid out. The exceptions are 
where certain pieces are worked from templets, and in these cases 
the templet is laid out from certain points on the casting, forging, 
punching, or whatever is used for the work in hand. 

Cutting Round Bars. The simplest form of laying out work is 
to be found in the centering of round bars that are to be turned in 
the lathe. In this case the end of the piece is chalked. Use a pair 
of hermaphrodite calipers; set the points A and B so that their 
distance apart is a little more than the radius of the piece. Place the 
caliper leg at three points on the circumference, A, B, and C , 


190 


MACHINE SHOP WORK 


179 


Fig. 250; and describe from each the arcs of circles A' A', B' B ', and 
C'C', respectively. Then, with the prickpunch, mark the point 
indicated by the small circle in the center. This will be the center. 
To test its accuracy, place the divider leg in the prickpunch mark, 
and see if the caliper leg will just touch the bar over its whole surface. 

Before drilling, the center should be emphasized with a center 
punch. 

The center square may be used for the operation of locating 
centers in round stock, as the center can be easily located at the 
intersection of two diameters drawn nearly at right angles. In some 
cases it is better to lay the shaft in V-blocks on a plate and use the 
surface gage, drawing at least two lines 
through the center of the piece. 

It is often necessary to cover the 
surface of the work where lines must be 
visible, with chalk, white lead, or cop¬ 
peras, before any laying out can be done; 
but in cases of this kind it is usual to 
mark directly upon the end of the bar. 

Before drilling, the center should be 
emphasized with a center punch. 

The locations for holes should be 
at the intersection of lines in order to be plain. After marking 
the center with a prickpunch, take a pair of dividers and describe 
a circle on the prepared surface concentric with the center already 
located. This circle should be about the diameter of the hole to be 
drilled; and in many good shops, it is the custom to draw another 
circle concentric with the first and about £ inch larger in diam¬ 
eter. This outer circle is called the reference circle, and is for 
the benefit of the inspector when it becomes necessary to place 
the responsibility for a misplaced hole. These circles may be 
marked with at least four prickpunch marks, as shown in 
Fig. 178; Part II, in order to indicate the position of the circle 
in case of the obliteration of the line. The center is then deep¬ 
ened by the center punch, and the hole drilled. In laying out 
centers upon rough castings, the first thing to do is to snag the 
work—that is, remove the ridges of the casting caused by the 
pattern being made in two or more parts. For small castings a 



Fig. 250. Centering Round Bar to 
be Turned in Lathe 


191 


180 


MACHINE SHOP WORK 


coarse file is generally used, while for large work the cold chisel is 
used. In many shops the cold chisel is operated by compressed air. 

Layout for Planer and Milling Machine. In laying out the work 
for the planer and milling machine, great care must be exercised. 

It is necessary that there 

_ __ £L - ^ - 1 should be a base line to 

|— _ jd I which the lines may be re- 

1 — _ . - ■ I ferred. It depends on the 

Fig. 251. Laying Out Valve Seats character of the Work ES to 

how this should be done. 
Sometimes it is quite sufficient to lay off the base line parallel to one 
side of the casting or forging. If the side thus used is to be finished, 
then the base line should be located at the proper distance from it to 
allow for the finishing. The amount required varies with the char¬ 
acter of the casting or forging; this has been fully explained. Usually 
there is some outline of the rough piece that will serve as a guide. 

As an example of 
the laying-out of work, 
take the valve and steam- 
chest seats shown in 
Figs. 251 and 252. The 
work is to be machined 
on a planer. The cylin¬ 
der has probably been 
bored. It is then placed 
on the planer, and so set 
that the center line 
through the cylinder is 
parallel to the platen of 
the planer. The first 
machine work to be done 
is the taking-off of the 
roughing cut from the 
face A. This face is to be planed down to a certain height above the 
cylinder center; this height may be marked on the edge of the valve- 
seat by the prickpunch mark B. If the surface C is to be planed at 
the same time, its height is indicated by the prickpunch mark D. 
These points may be located by means of the surface gage. Set the 


E 



r 

Fig. 252. Layout of Steam Ports 


192 


























MACHINE SHOP WORK 


181 


gage on the platen, and elevate the point to the proper height. 
Move it so that it will touch the side of the casting at the proper 
point, and make the marks B and D accordingly. When the surfaces 
A and C have received the roughing cut, the plan may be laid off 
as in Fig. 252. With a square having a suitable length of blade, 
locate the points G and H directly over the center of the cylinder. 
Cover the surfaces A and C with chalk where lines are to be drawn. 
Draw the lines I, J, 2v, and L on the surface A , between G and II. 
Through the center of the side of the exhaust port, draw the lines 
E and F at right angles to G H . This is done with a scriber. Lay 
off half the width of the exhaust port on either side of E and F, 
and draw the lines M N and OP parallel to E and F. In like manner, 
draw the lines QR and S T for the limits of the steam ports. All of 
these lines are to be emphasized by the use of prickpunch marks 
as indicated. 

If the sides of the valve-seat are to be finished, the line to which 
the metal is to be cut is indicated in the same manner. Finally, the 
holes VVV, etc., for the holding-down studs of the steam chest, are 
to be laid out. The center lines are first drawn; then the centers of 
the holes are marked, after which the circles for the holes are drawn 
as already described. 

Layout for Lathe. Work is rarely laid out for the lathe. It is 
not necessary that it should always be done for the planer. Laying 
out is employed where accuracy is essential, and where it is possible 
to secure the proper dimensions, with the piece to be operated upon 
in position on the machine. 

The man w T ho has charge of the work of laying out should have 
some knowledge of the elementary principles of geometry; he should 
also have some knowledge of drawing, and should, of course, be able 
to read drawings. 

General Suggestions. A few general suggestions may be given 
regarding work to be finished in the vise on either the planer, shaper, 
or milling machine, where several faces are to be finished at right 
angles to one another. Referring to the rectangular block of Fig. 253, 
the block is first placed in the vise with the face MNOP down, 
and the face MADP against the fixed jaw. The face ABCD is then 
machined, and the w T ork turned so that ABCD is against the fixed 
jaw, and MADP down. With the block in this position, NBCO 


193 


182 


MACHINE SHOP WORK 


is worked, making NBCO at right angles to ABCD. With ABCD 
still against the fixed jaw, and NBCO down, surface MADP is 
next worked. This brings two edges at right angles to the same side 
and parallel to each other. Then, placing ABCD down and either 
MADP or NBCO against the fixed jaw, surface MNOP is generated 
parallel to A BCD. This leaves the ends to be finished. The vise is 
swung so that the fixed jaw is at right angles to the line of motion 
of the tool; and on the planer and shaper they are finished by using 
the vertical feed. In the two last-named tools, the tool holder is 
swung so that the tool will clear the work easily on the return stroke. 

In working cast iron it is well to chamfer the edges with a file. 
If this is not done, the metal will break off when the tool reaches the 

end of the cut, leaving a 
ragged edge. The depth of 
the chamfer depends on the 
amount of metal to be re¬ 
moved. 

Fitting. Fitting is the 
term generally applied to the 
hand work necessary in 
assembling machinery after all 
the machine work has been done. Filing, either in the vise or 
lathe, and scraping, are the operations usually required, although 
the hammer and chisel are sometimes used. As hand work costs 
much more than machine work, the machining is done as closely as 
possible to make the hand work a very small item. 



SHOP SUGGESTIONS 

In the regular work of any shop, occasions are constantly arising 
for the determination of the best method of doing work. The success 
with which the desired end is attained depends upon the skill and 
judgment of the man in charge. While it is impossible in a limited 
space to give instructions regarding every possible emergency that 
may arise, a few suggestions regarding shop practice will be valuable. 

Peening. Peening consists in stretching the metal on one side of 
a piece of work in order to alter its shape. There is a wide difference 
between peening and bending. For example, suppose the curved or 
warped piece in Fig. 254 is to be straightened. If it were to be 


194 






MACHINE SHOP WORK 


183 


o 


1 




bent until it were straight, it would be placed on the block A with 
the concave surface down, as shown by the dotted lines. It could 
then be struck by the hammer and driven down past the line of 
support, and strained so that it would remain approximately straight. 
Such a method of straightening could not be applied to a piece of 
complicated outlines. It would remain wavy. In peening to trueness 
such a piece as shown in Fig. 254, it is laid on an anvil with the convex 
surface down. It is then struck with the peen of the hammer on the 
concave side. The blow must be quick and sharp. The result is 
that the metal is stretched at the point wdiere the blow is struck. 
By working successively over the whole surface, the concave side is 
stretched so that it is equal, in its dimensions, to the convex side. 
The piece then becomes straight, 
and will so remain. A skilful 
use of the hammer will straighten 
almost any piece of thin metal. 

Drilling Hard Metals. It is 
sometimes desirable to drill a hole 
in very hard metal. To do this 
the drill must be made very hard; 
it must be run at a very slow speed; it must be forced against the 
work as hard as possible without breaking the point; and it must be 
provided with an abundant supply of oil. For excessive hardening 
of a drill, it may be heated to a dull red heat, preferably in a charcoal 
fire, and quenched in mercury instead of water, in order to make 
the cooling more rapid. It will also assist in the operation, if the 
surface of the metal to be drilled is nicked with a cold chisel before 
work is begun. In some cases turpentine, in place of oil, may be used 
with beneficial results. 

Thin chilled cast iron may be softened by placing a small 
piece of sulphur on the place where a hole is desired, and then heating 
slowly to a dull red. 

Glass may also be drilled. There are two methods: one is to 
use a flat drill moistened with camphor and turpentine; and the 
other is to use a copper tube with No. 60 emery or carborundum and 
oil. In the last method, drill half-way through, reverse, and drill 
to meet, removing the fin at the center with a round file wet with 
water or turpentine. 


Fig. 254. Peening 


195 







184 


MACHINE SHOP WORK 


Grinding Valves. This is a kind of grinding that is usually 
done by hand. It consists in fitting a valve and its seat so that 
they are in metallic contact. In its results, it is the same as scraping. 
The process is very simple. The valve is coated with oil, and some 
fine emery sprinkled over it. It is then put on the seat and worked 
back and forth or revolved. The emery serves to grind off the high 
surfaces of both valve and seat. After grinding for a time, remove 
the valve, and wipe both surfaces clean. The metal on each will 
show where they have been in contact. When these indications 
appear over the whole of the surface, or in a continuous ring about 
the seat of a circular valve, the work is completed. 

Generating Surface Plates. In this operation it is necessary to 
work with three at the same time. For the sake of making the 
explanation clear, they will be called A, B, and C. After the plates 
have been planed, a straightedge should be laid on each. A straight¬ 
edge is merely a piece of flat steel having one or more edges true and 
straight. Set the straightedge on the plates in all directions. If it 
touches over its whole length in all positions, then the plates are 
ready for scraping. If it touches at the edges of the plate and is clear 
in the center, the former are high and should be filed down. If it 
touches in the center and rocks to and fro, the plate is convex and 
the center must be filed down. After the plates have been filed to 
trueness as far as trueness can be indicated by the straightedge, 
they are ready for scraping. 

Now take plates A and B and place them face to face. Strike 
a blow on the upper one, and it will cause a jarring sound to be 
heard. This shows that the two are not in perfect contact. Smear 
the surface of plate A with a thin mixture of red lead and oil. Cover 
the surface evenly and thinly. Then rub the two plates together, 
and where the red lead comes off onto the surface of plate B, the 
two come in contact. Take the scraper and scrape off a little of 
the metal from each of the plates where they have been in contact. 
Wipe off plate B; and again smearing plate A, proceed as before. 
Continue this process until the two surfaces are in contact over their 
whole areas. This does not prove, however, that they are flat. 
They may be in contact, as required, if A is convex and B is concave. 
To test this, the third plate is necessary. Smear plate B with red 
lead, and scrape C to fit it. Do not touch A. It is evident that A 


196 


MACHINE SHOP WORK 


185 


and C will then be alike. Bring them together. If they are both 
convex they will roll over each other. If they are concave they will 
bear at their edges, and not touch in the center. They will appear 
to be out of true by twice the actual amount. Scrape off the 
contact points of A and C. Remove as nearly as possible the same 
amount of metal from each. When these two plates have been 
brought so as to be in contact over their whole areas, lay plate 
aside, and scrape B until it fits C y but do not touch A. Try A and 
B together. If they do not touch over their whole areas, treat them 
as before described for A and C . Then introduce C again. Continue 
this alternating process until each of the three plates forms a bearing 
over the whole of the surface of 
each of the other two. 

During the latter part of the 
process, use alcohol instead of red 
lead. This will leave clean, bright 
spots at the points of contact. 

Fitting Brasses. This is a 
piece of work now usually done on 
a machine, but sometimes done by 
hand. Brasses which are to be 
used for connecting rods, and 
which are made in two pieces, as 
shown in Fig. 255, have a tendency to warp after the machine work has 
been done on them. The difficulty arises from their closing along the 
diameter A. Thus, if the brass is finished, and the hole bored out 
to the proper diameter, and is then cut apart on the line CD, it will be 
found, shortly afterward, that the diameter A is less than the 
diameter B. It may therefore be necessary to bore the hole somewhat 
larger than the working diameter. The kerf made by the saw will 
usually allow the parts to be drawn together along the diameter B f 
so that it will more than make up the shrinkage at A. The hole can 
then be scraped to fit the pin. The brasses should always be keyed 
solidly, metal to metal. This avoids a wear of the sides and edges of 
the metal, due to the thrust of the rod. 

Joints. Where a gas or liquid is to be retained in a pipe or 
other vessel without leakage, a tight joint is necessary. The method 
of grinding valves to their seats has already been explained. In that 



Fig. 255. Connecting-Rod Brasses 


197 











186 


MACHINE SHOP WORK 


case, it was shown that a metallic contact between the valve and its 
seat is all that is required in order to make it a tight joint. Two 
surfaces that have been scraped to fit will also accomplish the same 
purpose. This is frequently too expensive an operation to be per¬ 
formed, especially on rough work. In such places a softer material 
may be interposed between the two surfaces. Where the joint is to 
be a permanent one and is not to be taken down, the red lead joint is 
usually employed. This consists in the use of a mixture of red and 
white lead between the joints. To ordinary white lead ground in 
oil, add enough dry red lead to make a paste that can be spread 
without sticking to the blade with which it is applied. After the 
mixture has been made, it will be improved by pounding it well with 
the hammer. It may then be laid between the two pieces of metal 
forming the sides of the joint, and the latter be drawn together. 
Red lead joints are extensively used in pipe-fitting. The red lead 
has a tendency to rust the iron with which it is in contact, and thus 
forms a very tight connection between the two pieces. Where 
provision is to be made for taking down the joint at a future time, it 
is better to use a graphite paste made for the purpose. This does not 
rust the metal and it forms a perfectly tight joint, which may be 
taken down without difficulty at any time. 

Joints that are subject to occasional disconnecting can be best 
held by a disc of rubber packing. The latter is cut to fit the flanges 
between which the joint is to be made, and they are then drawn 
tightly together. 

Joints that are to be frequently taken down are usually packed 
with a piece of copper wire. Such a place is the joint between the 
steam chest and cylinder of a locomotive engine. A groove is cut in 
the two surfaces, and a copper wire is laid therein. This wire should 
be about \ inch in diameter. Its size, however, depends upon the 
joint to be packed. The ends of the wire are soldered together so 
that no leakage may occur past the ends. 

Another form of joint is the rust joint. This is always per¬ 
manent in character. The making of such a joint consists in rusting 
the two surfaces together. The following are the proportions by 
weight of the rusting material: 100 parts of iron turnings, 1 part of 
sal ammoniac, and f part of sulphur. The setting of the joint can 
be hastened by increasing the amount of sal ammoniac from 15 to 


198 


MACHINE SHOP WORK 187 

25 per cent. Mix the ingredients thoroughly, and just cover them 
with water. 

Fluting Rollers. Where feed rollers such as those used in wood¬ 
working machinery are to be turned and fluted, the turning should 
always be done first. This insures a continuous surface for the 
cutting tool. Where old rollers are to be re-turned and fluted, the 
same rule applies. The fluted surface may be turned to size. The 
lathe tool will break the edge of the ribs away; but when the fluting 
is done, these edges are again made smooth. The fluting can be done 
on a planer, with a round-nosed tool. The roller should be held on 
centers and clamped so that each groove may be presented to the 
tool in succession. A planer center, as illustrated in Fig. 190, Part II, 
affords a convenient method of holding and turning the work. 

Scale. Whenever a piece of cast iron is to be turned, the point 
of the tool should always be made to work beneath the scale. The 
scale is the hard outer shell that covers all cast iron as it comes from 
the foundry. It is very hard and brittle. If the edge of the tool is 
made to work in or against it, that edge will soon be dulled. If it is 
beneath it, the raising of the chip cracks and removes the scale. 

Pickling. Where castings are to be worked, either in the lathe 
or planer, to dimensions only a little less than those when rough, they 
should be pickled. This consists in washing them with a solution 
of sulphuric acid and water. The castings may be either submerged 
in or swabbed with the solution. The effect of pickling is to cause 
the scale to drop off in flakes, leaving the metal bare, unprotected, and 
rusty. The casting should then be washed with a sal soda solution. 
A good pickling solution for this work is to use 1 part of commercial 
sulphuric acid in 10 parts of water. 

Cold Chisels. It is well to use a coarser grade of steel for cold 
chisels than for lathe or planer tools. A coarse-grained metal is 
preferable because the continual hammering in use and redressing 
will gradually modify the granular structure until it is microscopic 
in texture. In dressing, it should never be heated above a cherry 
red, and the temper should be drawn well down so that the soft metal 
backs up the edge. A capacity to receive a multitude of grindings 
is not what is wanted. The tool must be able to endure the severe 
service for which it is intended. It must cut into a distorted mass of 
metal, where every blow gives it a shock tending to form a new 


199 


188 


MACHINE SHOP WORK 


arrangement of its particles. It never receives the steady pressure 
of the lathe tool; hence its powers of endurance must be greater. 

Lining Shafting. In equipping a shop, the first work of the 
machinist is the erection of the shafting. The main line should be 
the first laid out; and the engine, together with the jack and counter¬ 
shafting, must be located from it. After placing the hangers as 
nearly as possible in a horizontal line, the shafting should be placed 
in the boxes and attached to the hangers. For lining the shaft, a 
level and a fine grass or silk line are indispensable. The line is tightly 
drawn, horizontally, a short distance from the position the shaft is 
intended to occupy, and the distance from the surface of the shaft 

to the line is measured and 

______made equal near each hanger 

_ stick _by a stick such as shown in 

Fig. 256. Gage for Parallel Lining of Shafting 

The level is used to 
make the shaft horizontal; and, if the hangers are adjustable in two 
planes, the operation is quite rapid. 

When other shafting is to be erected parallel to the first, if the 
distance does not exceed twelve or fifteen feet, a long stick may be 
used by driving a nail into the end of the stick to allow some adjust¬ 
ment. The level is used as before. 

When the distance is great, or obstacles prevent the use of the 
stick as suggested, a line may be drawn on the floor of the shop by 
dropping a plumb line from near the ends of the first shaft and 
connecting the points located. Another line, directly under the 
desired location, may be drawn by direct measurement, and the 
second shaft erected by dropping a plumb line to this second floor 
line near the ends of the second shaft. This method may be employed, 
with such variations as the case may demand, even though a floor or 
wall be between the locations. 

In leveling up long lines, or around machines, or through walls, 
the hydrostatic level is a most convenient tool. It consists of two 
graduated glass tubes set in suitable bases and connected by a 
rubber tube. When the rubber tube is filled with water, and the 
glass tubes placed vertically on the shaft, the fluid should stand at 
the same graduation in each glass. These levels are made with self¬ 
acting valves to prevent the escape of the fluid. 


200 



MACHINE SHOP WORK 189 

When pulleys or hangers make the direct application of a level 
to the shaft impracticable, leveling hooks, in connection with a 
wooden straightedge, as shown in Fig. 257, are very convenient. 
These may be made of wood or metal, and of lengths suitable to the 
case in hand. 

Machine Setting. After the shafting is erected, comes the 
setting of machines. The countershafts are first erected parallel to 
the main line, and with due regard to the location of the machine. 
The machine is then placed, with its driving shaft parallel to the 
counter, by use of the plumb line; and the platen, table, or other 
horizontal surface carefully leveled, in two planes, by wedging up 



Fig. 257. Method of Using Level for Lining Shafting 


the machine with common shingles. The machine is then secured 
to the floor by lag screws. 

When the machines are very heavy, and stone or masonry 
foundations are necessary, anchor bolts are built into the foundation 
at suitable points, or holes drilled for expansion bolts. The machine 
is then lined and leveled as already suggested. The bottom of the 
machine, however, is usually a rough casting; the top of the stone 
foundation is still rougher; and, as the wedges are likely to slip out 
under the jarring of the machine, a permanent support must be 
provided. This may be done by pouring melted sulphur beneath 
the bed. To do this, build a dam of clay or sand all around the bed 
and about 2 inches high. Melt ordinary stick sulphur or brimstone 
in ladles, and pour in at several points at once. Keep the space 
flooded until the dam is well filled, and allow it to harden. This will 


201 
































190 


MACHINE SHOP WORK 


occur very quickly, after which the dam may be removed and the 
sulphur cut away from the edge of the machine. Care must be 
taken that the temperature of the sulphur is as high as possible 
before pouring. Unless this is done, it will cool and set before reach¬ 
ing the inmost recesses beneath the machine. It will then crumble 
because of insufficient bearing surface to carry the imposed weight. 
The sulphur having been properly placed and having set, the nuts 
are then screwed down on the bolts, and the machine is secure. 

Belting. The shafting and machines are usually driven by belt¬ 
ing. Leather is the material generally used, and the belting may be 
from single to six-ply in any suitable width. Single belting has a 
flesh and a grain or hair side, and should be run with the grain side in 
contact with the pulley. The ends are cut square, and fastened by 
hooks, coiled wire, or rawhide lacing. 

Leather belting is injured by water, steam, oil, and temperature 
above 110° F. Where such conditions exist, cotton belts faced with 
thin leather, or rubber belts, may be used. These belts are cheaper 
than leather, are about as strong, and will transmit power as effec¬ 
tively; but they will not stand mutilation of the edges. This is a 
point of prime importance, and prohibits their use in many cases. 

The power transmitted by a belt is directly proportional to its 
speed and width. A safe rule is to allow one horsepower for a speed 
of 1,000 feet per minute, with a single thick belt one inch wide. This 
is a more liberal allowance in favor of the belt than is usually given, 
but will increase the life of the belt in far greater proportion than the 
increase in first cost. Double belts will transmit about one and one- 
half times as much power as single belts. The above rule applies to 
belts running over pulleys of equal diameter, or, in other words, to 
cases where the arc of contact is 180 degrees. For smaller arcs of 
contact, use the coefficients found in the following tabulation: 

Degrees: 90 100 110 120 130 140 150 160 170 180 200 

Coefficient: .65 .70 . 75 . 79 . 83 . 87 . 91 .94 . 97 1. 1.05 

To increase the power transmitted, either increase the speed of 
the belt by using larger pulleys, or use a wider belt. 

Example. A 3-inch single belt is running over a 24-inch driving 
pulley which makes 200 r.p.m. (revolutions per minute). How 
many h-p. will it transmit? 


202 


MACHINE SHOP WORK 


191 


Solution. The circumference of the pulley in feet is 2X3.1416 = 
6.2832 feet. As the speed of the pulley is 200 r.p.m, the speed of 
the belt will be 200X6.2832 = 1,256.64 feet per minute. For every 
inch of width, it will transmit 1,256.64-^1,000 = 1.25664 h-p. 
Then a 3-inch belt will transmit 3X1.25664 = 3.76992 h-p. 


Ans. 3.75 h-p. (approximately) 
Example. It is desired to increase the h-p. in the above example 
to 5 h-p. How may it be done? 

Solution, (a) By using a wider belt in the proportion of 
3.75 to 5. 3.75 : 5 : : 3 : 4. Ans. By using a 4-inch belt 

(b) By using a larger pulley in the same proportion. 3.75 : 

5 : : 24 : 32 * Ans. By using a 32-inch pulley 

(c) . % using a double belt. 1 :1.5 : : 3.75 : 5.63. This would 
give a little better result than required. 


203 








FELLOWS GEAR SHAPER CUTTING SPUR GEAR 

Courtesy of Fellows Gear Shaper Company, Springfield , Vermont 




























MACHINE SHOP WORK 


PART IV 


GEAR CUTTING 

Theory of Toothed Gearing. The fundamental principle of 
toothed gearing is that of two cylinders or portions of cones with their 
surfaces in contact, and rolling together in opposite directions. 

The first condition, that of cylinders, is shown in Fig. 258, 
representing the two cylinders A and B, the axes of both being in the 
same plane and parallel, and the periphery of the cylinders in con¬ 
tact. It is evident that if the cylinder A be rotated in the direction 
of the arrow, the frictional contact will cause the cylinder B to 
rotate in the opposite direction. 

The second condition, that of cones, is shown in Fig. 259, rep¬ 
resenting the two cones A and B, the axes of both being in the same 
plane, but at right 
angles to each other, and 
the outer surfaces of the 
cones in contact. The 
action is the same as 
that of Fig. 258. 

It will also be evi¬ 
dent that if the cylin¬ 
ders in Fig. 258 are of equal diameters, and consequently of equal 
circumferences, the rotation of A through a complete revolution will 
produce a complete revolution of B. If A is one-half the diameter 
of B, the latter will make but half a revolution to one complete 
revolution of A; while, if the cylinder B is one-half the diameter of 
A, it will make two complete revolutions to one of the cylinder A. 

This proposition provides for no slipping of the cylinders on 
each other. For the purpose of transmitting power, the faces of 
these cylinders are provided with teeth, which are cut parallel to 
the axes of the cylinder; the teeth of each cylinder interlock with 
those of the other and effectually prevent any slipping. By this 



Fig. 258. Two Cylinders in Contact 


205 










194 


MACHINE SHOP WORK 


means we produce a pair of spur gears. In the case of the two 
cones, or a suitable portion of them, if the teeth are formed 
radiating from the apex of the cone, they become a pair of bevel gears. 



The simplest form and the one in most common use, is the spur 
gear. All other forms are but modifications of it in one way or 
another, the general principle and the principle upon which the teeth 
are formed being practically the same in every form of gear in use. 



It therefore becomes necessary to study carefully the essential 
features of the spur gear, and to understand thoroughly its con¬ 
struction. 

It being one of the conditions of the problem that the surfaces 
of the cylinders shall remain in contact, as shown in Fig. 258, teeth 


206 















MACHINE SHOP WORK 


195 


must not be formed in their surfaces by cutting grooves in them, for 
the reason that, to cause the teeth to interlock, it would be necessary 
to move their axes closer together, thus overlapping the original 
surfaces. Teeth cannot be added to the cylinders as this would 
necessitate moving the cylinders farther apart, thus separating the 
contact surfaces. 

This being the case, the teeth must be formed by a combination 
of both the above methods, cutting the grooves one-half the depth of 
the proposed teeth,, and adding between the spaces thus formed an 
equal amount to complete the partially formed teeth. They will then 



present the forms shown in Fig. 2G0, the added portions being dis¬ 
tinguished by being drawn solid instead of being sectioned. They 
are called the addendum. 

The teeth now interlock properly by falling into the spaces, the 
original surfaces of the cylinders remaining on the contact line; and 
the diameters of these cylinders still give the base circles for all 
calculations as to speed, numbers, and dimensions of teeth and 
similar purposes. These circles are called the pitch circles. When 
a pair of gears vary in diameter by a ratio of 1 to 3, or more, the 
larger is called the wheel, and the smaller the pinion. 

Names of the Tooth Parts. The names of the tooth parts are 
given in the diagram, Fig. 261, in order that the student may become 
perfectly familiar with the technical terms used in describing or 


207 






196 


MACHINE SHOP WORK 


referring to the teeth of gears, and the methods of calculating, 
designing, and drawing their various parts. 

The 'pitch diameter is the diameter of the pitch circle. 

The addendum circle has the same diameter as the outside diam¬ 
eter—that is, the diameter over the points of the teeth. 

The dedendum circle, or root circle, is the circle at the bottom of 
the teeth. 

The pitch is the distance from center to center of the teeth when 
measured on the pitch circle. When thus measured, it is called the 
circular pitch. 

The face of the tooth is that portion of the curve outside of the 
pitch circle. 

The flank of the tooth is that portion of the curve within the 
pitch circle. 

The thickness of the tooth is its width, taken as the chord of an 
arc of the pitch circle. 

The space is the distance between adjacent teeth, measured as 
the chord of an arc of the pitch circle. 

DESIGNING GEARS 

Fixed Pitch Method. Formerly the teeth of gears were designed 
on the basis of a fixed distance representing the pitch. This was 
usually based on the common fractions of an inch or multiples of 
them, as J, f, \, f, f, f, 1,If, 1§, If, 2, 2\, 3 inches, etc. The desired 
number of teeth multiplied by the given pitch gave the circum¬ 
ference; and the distance thus found divided by 3.1416 gave the 
diameter of the pitch circle. 

The pitch was divided into 15 parts, 7 of which represented the 
thickness of the teeth and 8 the width of the space. To find the 
length of the teeth, the pitch was divided into 10 parts, of which 
seven represented the length of the teeth—3 parts being that portion 
outside of the pitch circle and 4 parts the length inside of it, 1 part 
being allowed for bottom clearance. Such a method involved many 
tedious calculations, and in due time mechanical engineers devised 
a method simpler and more convenient, which has of late years 
been exclusively used for this purpose. 

Diametral Pitch Method. By this system the pitch is desig¬ 
nated by a number instead of giving the length of the pitch in inches. 


208 


MACHINE SHOP WORK 


197 


This number indicates the number of teeth for each inch of diameter of 
the 'pitch circle. Therefore, if the diametral pitch is 6, and the 
diameter of the pitch circle is 10 inches, the gear will have 6X10, 
or 60 teeth. Thus we know that if the pitch is 6, or, as usually 
expressed, “6 pitch”, and the gear has 60 teeth, the pitch diameter is 
60-^6, or 10 inches. And if the gear has 60 teeth, and the diameter 
of the pitch circle is 10 inches, the pitch is 60^10, or 6 pitch. We 
have then the three following simple rules: 

(1) Multiply the diameter of the pitch circle by the diametral pitch 
to get the number of teeth. 

(2) Divide the number of teeth by the diameter of the pitch circle to 
get the diametral pitch. 

(3) Divide the number of teeth by the diametral pitch to get the 
diameter of the pitch circle. 

The proportions of tooth parts are determined by methods quite 
as simple as the question of pitch. They are as follows: 

The addendum is equal to one inch divided by the diametral 
pitch; hence that on a 6-pitch gear will be J of an inch. 

The dedendum is a like distance increased by the clearance, 
which is equal to one-tenth of the thickness of the tooth on the 
pitch circle. 

The thickness of the tooth, and the width of the space at the 
pitch line, are not determined by a rule similar to that given in the 
former method. In accurately cut gears, the width of the space 
exceeds the thickness of the tooth by only as much as may be neces¬ 
sary to permit the gear teeth to roll freely together, and need nqt be 
over .03 of the circular pitch. In cut gears for ordinary purposes, 
this amount may be doubled; wdiile in gears having cast teeth, it may 
need to be as great as 0.10 of the circular pitch depending, of course, 
upon the accuracy of the casting. 

In order to afford a correct impression of the relative dimensions 
of spur-gear teeth of different diametral pitches, Fig. 262 is given, 
in which the gear teeth are shown full size. These are the more 
common pitches. Those larger than here shown are usually 1, 1J, 
2, 2 \, and 3 pitch. 

Development of Gear=Tooth Curves. Epicycloidal Curve. 
This is a matter of considerable importance, and should be thor¬ 
oughly understood in connection with the work of gear cutting. 


209 


MACHINE SHOP WORK 



Fig. 262. Proportions of Teeth of Different Diametral Pitches 















MACHINE SHOP WORK 


199 


Formerly the epicycloidal curve was considered to be the most 
appropriate, since it is traced by a fixed point in the periphery of 
one cylinder rolling upon another. This is a perfectly correct 
theory, and many excellent gears are still made with this form of 
teeth. 

There is one serious disadvantage, however, in gears with teeth 
so formed. In gears of much variation in diameter the teeth are so 
different from each other in form that they will not run properly with 
other gears varying much in diameter from the particular gear 
designed to run with them. The result was a great variety of curves 
in gears w ith cast teeth, and of cutters, when the teeth were cut from 
solid blanks, which often proved very troublesome and expensive; 
and many efforts were made to produce some more satisfactory 
method. 


Involute Curve . The involute curve was experimented with, 
and satisfactory results were obtained. It possesses several advan¬ 
tages over the epicycloidal curve, which may be stated as follows: 
A single curve is sufficient, while in the epicycloid a com¬ 
pound curve was necessary. 

Undercutting the flanks of the teeth is not necessary. 

Gears of any number of teeth will run properly with other 


gears of any number of teeth indiscriminately. This 
is a very great advantage in many respects. 

Cutters properly formed to cut involute teeth may be used for 
gears of a considerable variation as to numbers of teeth. This fact 
greatly reduces the number of cutters of each pitch that are required 
or cutting a complete range of work from pinions of 12 teeth to a 
rack. Where 8 cutters are required, the ranges of work are as follows: 
No. 1 will cut from 135 teeth to a rack 
No. 2 will cut from 55 teeth to 134 teeth 
35 teeth to 54 teeth 
26 teeth to 34 teeth 
21 teeth to 25 teeth 
17 teeth to 20 teeth 
14 teeth to 16 teeth 
12 teeth to 15 teeth 
The involute curve is generated mechanically by a point at the 
nd of a cord which is unwound from the surface of a circular disc 


No. 3 will cut from 
No. 4 will cut from 
No. 5 will cut from 
No. 6 will cut from 
No. 7 will cut from 
No. 8 will cut from 


211 


200 


MACHINE SHOP WORK 


or a cylinder. The curve is generated as shown in Fig. 263. A is 
an arc representing the cylinder, with its center at B . From the 
vertical line BC, and on the arc A, are spaced at equal distances the 
points 1,2, 8, 4, 5, 6, 7,8. Radial lines are drawn from each of those 
to the center B. From each of these points are drawn the lines a, b, 
c, d,e,f, g, which are tangent to the arc A . From 2 as a center, and 
with the distance 1-2, the portion of the required curve from the arc 

to the line a is traced. 
From 8 as a center, with 
the distance 1-3, the por¬ 
tion [of the curve from a 
to b is traced. And so 
on, until the involute 
curve D is traced as far 
as may be necessary. 

In the practical use 
of the involute curve thus 
determined, an arc of 
such radius, and with its 
center so located as to 
approach closely the true 
curve, is generally used, 
and forms not only the 
face but the flank of the tooth. For this purpose, gears are classi¬ 
fied according to the number of teeth as follows: 

First Class — all gears having over 30 teeth 
Second Class —all gears having 19 to 29 teeth, inclusive 
Third Class — all gears having 12 to 18 teeth, inclusive 

Laying Out Teeth. The method of laying out teeth of the first 
class is shown in Fig. 264. The pitch circle A has its center at B, 
upon the vertical line BC. From this center the addendum circle D 
and the dedendum or root circle E are drawn. From the vertical 
line BC, and to the right and left on the pitch circle A, are laid off 
the centers of the teeth, and the radial lines 1, 2, 3, 4, 5 drawn. 
Through a, the point of intersection of the vertical line BC and the 
pitch circle A, is drawn the arc F, of one-half the radius of the pitch 
circle. Through the point of intersection b of this arc with the 



212 





MACHINE SHOP WORK 


201 


radial line 4 —equal to the pitch from the vertical line BC —the base 
circle G is drawn. To the left of the vertical line BC and on the 
pitch circle A, is set off one-half the thickness of the tooth—one- 
fourth the pitch—to the point c. With a radius equal to be, and 
from b as a center, the arc d is drawn, representing the face and flank 
of one side of the center tooth. With the same radius, and with 
the intersections of the radial lines 1 , 2 , 8 , 4 , and 5 with the base 



circle G, the arcs representing the faces and flanks of the other teeth 
are drawn. The bottom clearance is equal to one-tenth the thick¬ 
ness of the tooth on the pitch circle; therefore the arcs d are brought 
down to within this distance of the dedendum or root circle E and 
completed with a small arc of a radius equal to the clearance. This 
method is adapted to the teeth of gears of the first class (30 teeth or 
over), and will be found applicable to gears cut from solid blanks or 
those with cast teeth, making proper allowance's for clearance in 
the latter case. 

Gears of less than 30 teeth comprise the other two classes. It 
is readily seen that as the gears are very much reduced in diameter, 


213 










202 


MACHINE SHOP WORK 


the angle at which the teeth of one enter the spaces of the other will 
require a modification in the form of the teeth. 

The method of form¬ 
ing the teeth of gears of 
the second class is shown 
in Fig. 265. This method 
proceeds in the same 
manner as shown in Fig. 
264 and described above, 
up to the location of the 
center for the arc form¬ 
ing the face of the tooth. 
In the former case, this 
was at the intersection of 
the arc F with a radial 
line drawn through the center of the adjacent tooth. In this case 
it is located at the intersection of the arc F with a radial line drawn 
through the center of the space. The curve d is therefore of rela¬ 
tively shorter radius. Instead of prolonging the curve d to the 



Fig. 265. Laying Out Gears of Second Class 



clearance arc, the flank of the tooth is formed by straight lines ff 
parallel to the vertical line BC and tangent to the curve d. 

The method of forming the teeth of gears of the third class is 
shown in Fig. 266, and follows the method shown in Fig. 264, up to 


214 











MACHINE SHOP WORK 


203 


the location of the center for the arc forming the face of the tooth. 
In this case it is located midway between the position shown in 
Fig. 264, and that in Fig. 265, otherwise at the intersection of the 
tooth curve d with the base circle G; and the flanks of the tooth are 
radial instead of parallel lines. 

These three methods of describing the forms of involute teeth, 
for the three classes described, produce curves very closelv corre¬ 



sponding to the theoretically correct involute curves, and quite 
sufficient for all practical purposes for which gears having teeth cut 
with circular cutters are intended. 

Internal Gears. Internal gears must frequently be used when 
there is not room for spur gears, or when the nature of the work or 
the design of the machine of which they are a part renders this form 
necessary or advisable. Thus far we have considered gears repre¬ 
sented by cylinders whose outer surfaces rolled together. In the case 


215 










204 


MACHINE SHOP WORK 


of the internal gear the outer surface of a smaller cylinder is supposed 
to roll on the internal surface of a larger cylinder. Therefore, 
the larger gear will have teeth projecting inwardly or toward its axis. 

Theoretically the proper curve for the teeth of an internal gear 
will be the internal epicycloid, as this is the curve traced by a point 



on the surface of one cylinder rolling inside of another cylinder. 
The method of laying out the teeth is shown in Fig. 267. The pitch 
circle A y addendum circle D, and dedendum circle E are drawn as 
in the previous examples, the vertical line BC indicating the center 
of the work. The pitch is spaced off on the pitch circle A, each way 
from the line BC, and the thickness of the teeth and width of the 



spaces indicated. At the point of intersection of the vertical line 
BC with the pitch circle A , is drawn an inclined line FF at an angle 
of 78 degrees to the vertical line BC. Through the point of inter¬ 
section a of this line with the center line 4 of the adjacent tooth, the 
base circle H is drawn, giving the location of the centers for the 
faces of the teeth, which are described by the arc of the radius ob. 


216 























MACHINE SHOP WORK 205 

In a similar manner the line GG is drawn at an angle of 87 degrees 
with the vertical line BC; and through the point of intersection c 
with the radial line 4, the base circle J is drawn, which gives the loca¬ 
tion of the centers for the flanks of the teeth, which are described by 
the arc of the radius cd. The arc joining the flank curve with the 
dedendum circle is the same as in previous examples. 

Teeth of Racks. Two methods are in use for drawing the form 
of teeth for racks. The first method is shown in Fig. 268. The pitch 
line A, addendum line B, and dedendum line C are straight lines 
located as before described. The teeth and spaces are set off at 
equal distances on the pitch line A . The sides of the teeth, including 
face and flank, are composed of straight lines aa inclined at an angle 
of 14J degrees from a vertical line or 75§ degrees from the pitch line A. 
The lower ends of these lines are joined to the dedendum line by 
small arcs, as previously described. While this form of tooth is not 
theoretically correct, many racks running with gears having involute 
teeth are so constructed, and they operate satisfactorily for many 
kinds of work. However, the second method, Fig. 269, is preferable 
for accurate work and for carrying heavy loads. The principal 
lines A, B } and C , and the spacing of the teeth are the same as in 
Fig. 268. The vertical line DD is erected at the side of one of the 
teeth. Through the point a of the intersection of this line with the 
pitch line A is drawn the inclined line EE at an angle of 78 degrees 
with the vertical line DD. Through the point 6 of the intersection 
of this line with the vertical line 8 of the side of the adjacent tooth 
is drawn the base line F, which locates the centers for the arc with 
the radius 6c, forming the face of the tooth. Through the point d 
of the intersection of the line EE with the vertical line 2 , at the left 
of the tooth, the base line G is drawn, locating the centers for the 
arc with the radius de, forming the flank of the tooth. The lower 
ends of these arcs are joined to the dedendum line C by small arcs, 
as previously described. 

Table X gives the various dimensions of the parts of gear teeth 
calculated for involute teeth designed upon the diametral-pitch 
system. It is useful in comparing the different dimensions of the 
same pitch with one another, and in comparing similar dimensions 
used in the same pitch; and it will enable the student to avoid 
making tedious calculations in each instance. 


217 


206 


MACHINE SHOP WORK 


TABLE X 


Involute Gear Tooth Parts 


Diametral 

Pitch 

Circular 

Pitch 

Thickness 
of Tooth 

Addendum 

Working 

Depth 

Whole 

Depth 

1 

3.1416 

1.5708 

1.0000 

2.0000 

2.1571 


2.0944 

1.0472 

.6666 

1.3333 

1.4381 

2 

1.5708 

.7854 

.5000 

1.0000 

1.0785 

21 

1.2566 

.6283 

.4000 

.8000 

.8628 

3 

1.0472 

.5236 

.3333 

.6666 

.7190 

4 

.7854 

.3927 

.2500 

.5000 

.5393 

5 

.6283 

.3142 

.2000 

.4000 

.4314 

6 

.5236 

.2618 

.1666 

.3333 

.3463 

7 

.4488 

.2244 

.1429 

.2857 

.3080 

8 

.3927 

.ly63 

.1250 

.2500 

.2696 

9 

.3491 

.1745 

.1111 

.2222 

.2396 

10 

.3142 

.1571 

.1000 

.2000 

.2157 

12 

.2618 

.1309 

.0833 

.1666 

.1796 

14 

.2244 

.1122 

.0714 

.1429 

.1540 

16 

.1963 

.0981 

.0625 

.1250 

.1348 

18 

.1745 

.0871 

.0555 

.1111 

.1198 

20 

.1571 

.0785 

.0500 

.1000 

.1078 

24 

.1309 

.0654 

.0416 

.0833 

.0898 


Attention is directed to the following characteristics of these 
dimensions: 

(a) The thickness of the tooth equals one-half the circular pitch. 

(b) The addendum equals 1 (one inch), divided by the diametral pitch. 

(c) The working depth of the tooth is twice the addendum, as the adden¬ 
dum and dedendum are equal. 

(d) The whole depth of the tooth is the working depth plus one-tenth 
of the thickness of the tooth, which is the clearance. The radius of the clear¬ 
ance arc is one-seventh of the distance between the points of adjacent teeth. 




Bevel Gears. In the treatment of spur gears, we have consid¬ 
ered them fundamentally as cylinders rolling upon each other (ordi- 


218 



























MACHINE SHOP WORK 


207 


nary spur gears) or a cylinder rolling on the inner surface of a larger 
one (internal gears). W e now come to consider cones of various 
diameters and relative proportions rolling together, as shown in 
Fig. 2o9. The surfaces of the cones represent their pitch circles in 
the same manner as the cylinders. While spur gears must have their 
shafts always parallel, bevel gears may be designed to run properly 
at any angle from parallel to 150 degrees. In Fig. 270 are shown 
several pairs of typical bevel gears with their shafts at different angles. 
Those of 90 degrees are the more common. The pair shown at 4 



Fig. 271. Cross-Section of Pair of Bevel Gears 

are unusual but sometimes necessary, and operate quite as well as 
the others. In this case the larger gear is an internal bevel gear. 

When two bevel gears of the same diameter and number of teeth 
run together, they are called miter gears,* although this term is more 
likely to be applied to those whose shafts-are at an angle of 90 degrees 
to each other. 

Fig. 271 is a cross-section of a pair of bevel gears, and is designed 
to illustrate the principles applicable to the cutting of gears. The 
lines A A and BB are the center lines of the two shafts, their point 
of intersection being the apex of each of the cones representing the 
pitch surfaces. The line CC is parallel to A A and at a distance from 
it equal to half the pitch diameter of the larger gear. The line D D 


219 



























208 


MACHINE SHOP WORK 


is parallel to the line BB, and distant from it one-half the pitch diam¬ 
eter of the smaller gear. Between the points of intersection of the 
lines ^4^4 and BB, and of CO and DD f the pitch line EE is drawn, 
giving the line of contact between the two cones. The outline of the 
cones is completed by the line FF. The outer and inner ends of 
the teeth are lines at right angles to the pitch lines; and upon the 
outer tooth lines the depths of the teeth above and below the pitch 
lines are set off; and the lines a and b, for the top and bottom of the 
teeth, are drawn radially from the common apex of the cones at c. 
The various dimensions of the teeth are laid off at the large or outer 
ends of the teeth, and are taken from Table X. 

To facilitate the proper cutting of bevel gears, the drawing should 
give the face angle a and the cutting angle b for each gear, and 
the depth of the teeth at the outer end. The angles should be so 
expressed that a bevel protractor may be set against the hub of the 
gear, and its arm upon the face angle and cutting angle, to verify 
their correctness. When the shafts are at right angles, the sum of 
the edge angles will equal 90 degrees, and the sum of the face angles 
and edge angles will be equal. 

The angles may be determined by this method, for the angle of 
the pitch line FF with the face of the hub (or the line DD parallel 
to it), we may consider as a right-angled triangle FFD. Divide 
the height by the base, and the quotient will be the natural tangent. 
From the table of tangents we get the angle in degrees and minutes. 

Thus, suppose the base is 5 inches, and the height 2.5 inches, 
then 2.5 5 = 0.5, which is the tangent. In the table of tangents we 
find the nearest number is .50004, whose corresponding angle is 26 
degrees 34 minutes. The value of any angle expressed in degrees and 
minutes may be determined in the same manner if the base and 
height are known. 

Worm Gearing. This is a term used to describe the device 
consisting of a gear similar to a spur gear driven by a worm—that is, a 
cylinder upon whose surface is a thread fitting into the teeth of the 
gear. The relative speed of the worm and gear are found by dividing 
the number of teeth in the gear by the number of threads on the 
worm. Worms are always understood to be of single thread, unless 
otherwise specified. The pitch of a single-threaded worm is equal 
to the circular pitch of the worm gear, and vice versa. The shafts 


220 


MACHINE SHOP WORK 


209 


of a worm and worm gear are usually (but not necessarily) at right 
angles to each other. 

A simple form of worm gear is shown in Fig. 272, in which the 
worm B has a single thread having an inclination on each side of 14f 
degrees, or what is usually called a “29-degree” thread. The teeth 
of the worm are cut to a similar form, and the pitch circle located the 



same as in a spur gear; but, as the lines of the thread of the worm are 
not at right angles to the axis, but at an angle due to the pitch of the 
thread, the teeth of the worm gear must be cut at such an angle as to 
be tangent to the curved line of the thread, as shown at a. The 
calculations for this worm gear are made the same as for a spur gear. 
Thus the pitch of the thread, multiplied by the number of teeth, will 
give the circumference of the pitch circle, which amount, divided by 
3.1416, will give its diameter. In consequence of the relatively large 


221 











































210 


MACHINE SHOP WORK 


diameter of the worm compared with the thickness of the worm gear, 
enclosing an angle of only 14 degrees on the pitch line, the teeth of 
the latter may be cut on a line parallel to its axis, as they will con¬ 
form quite nearly to the curvature of the thread of the worm. This 
is the simplest form of a worm gear, and one not often used, on 
account of the small amount of power it is able to transmit. 

The usual practice, particularly where considerable power is 
to be transmitted, is to design the worm wheel as shown in Fig. 27S, 

by which a much greater area of 
contact is secured, but making a 
much more complicated form, 
and one in which some new con¬ 
ditions must be considered. In 
this case the enclosing angle is 
80 degrees, instead of 29 degrees, 
as in the former example. In 
the former example, the teeth 
were cut as in a spur gear, hence 
the pitch surface bb, Fig. 272, 
was straight, and the diameter 
of the pitch circle was therefore 
measured as in a spur gear. In 
this case the pitch line is con¬ 
siderably curved, being an 80- 
degree arc on the pitch circle a 
of the worm. It has sometimes 
been the practice to calculate the pitch diameter from the point b, 
usually called the throat of the gear. It is obvious that this is an 
arbitrary point, that the number of degrees contained in the enclos¬ 
ing angle is not considered, and that, for instance, if the number of 
degrees were much reduced, so as to materially flatten the arc, this 
point would vary considerably from its proper place. It has been 
found in practice that if we divide that portion of the pitch line a 
that lies between the vertical center line xy and the enclosing angle 
into three equal parts as shown, whatever may be the enclosing 
angle, the point c will indicate the correct diameter of the pitch 
circle. We shall then have the pitch diameter at C, the diameter 
at the bottom of the teeth at D, and the outside diameter at E. 



Fig. 273. Worm Gear with Large Enclosing 
Angle 


222 



















MACHINE SHOP WORK 


211 


These relative diameters bear no fixed relation to similar dimen¬ 
sions of a spur gear, or to those of other worm gears of differing 
proportions. 

To find the angle of the thread, we use the right-angled triangle, 
as shown in Fig. 274, in which the base equals the circumference of 
the worm, the height equals the pitch of the thread, and the hypothe- 
nuse is the development of the thread itself. Mathematically we 
find the angle of the thread by dividing the pitch (height) by the 
circumference (base) to get the tangent of the arc, and obtain the 
angle from a table of natural tangents. Should the worm have a 
double thread, the height of the triangle will be twice as great. 

Spiral Gears. As has heretofore been stated, the spur gear has 
its teeth cut in a line parallel to the axis. If the teeth are cut at an 



C ircum ference 

Fig. 274. Diagram for Finding Angle of Worm Thread 


angle to the axis, and the cut continued by the gradual rotation of the 
gear blank as it advances, a spiral gear will be produced. If the cut 
is prolonged, it will finally make a complete revolution and arrive 
at the original line parallel to the axis of rotation. The lead of the 
spiral is the distance from the beginning of the cut to a point where 
the revolution is completed. The angle of the spiral is found in a 
manner similar to that described for the diagram, Fig. 274. As 
applied to this case, the rule will be: divide the number of inches of the 
circumference of the cylinder on which the spiral is to be cut by the 
number of inches in the lead, and the quotient will be the tangent 
of the angle of the spiral, the angle being found from a table of 
natural tangents. Thus we have the following rule: Divide the 
circumference by the tangent of the angle to produce the lead; or multiply 
the tangent by the lead to produce the circumference . 

In making calculations for spiral gears, the pitch diameter, 
and not the outside diameter, is understood. Spiral gears have 
several properties that should be remembered in making calcula- 


223 




212 


MACHINE SHOP WORK 


tions for them. It is assumed in each case that the gears are engaged, 
or in mesh, with one another. 

(1) Two spiral gears of equal diameter, number of teeth, and angle of 
teeth, will have the same lead of spiral. 

(2) If two spiral gears are of equal diameter, one having twice as many 
teeth as the other, one will have twice the length of lead of the other. 

(3) If two spiral gears are of equal diameter, one having twice as many 
teeth as the other, the teeth of one will have twice the angle of the other. 

(4) Two spiral gears of equal diam¬ 
eter, on parallel shafts, will have the same 
angle of te6th on both. 

(5) Two right-hand spiral gears must 
have the angles of their shafts at an angle 
equal to the sum of the angles of the teeth 
of both gears. 

(6) One right-hand and one left-hand 
spiral gear must have the angles of their shafts 
equal to the angle of the teeth of one gear, 
less the angle of the teeth of the other. 

(7) If two spiral gears are of equal 
diameter, one with twice as many teeth as the 
other, the gear with the lesser number of 
teeth will have them at twice the angle of 
the other. 

(8) If one of two spiral gears has teeth 
at an angle of 45 degrees the other having 
twice the number of teeth, its lead will be 
twice as great and its pitch diameter twice 
that of the other. 

(9) Diameters being equal, double the 
number of teeth indicates ‘one-half the angle 
and vice versa . 

(10) If the angles of teeth are equal, 
either gear may be the driver. If the tooth 
angle in one gear is twice that in another, it 
must be the driver. 

Fig. 275. Simple Form of Spimi Gears The lines representing the angles 

of the teeth of spiral gears must be 
tangents to the side of the tooth at the pitch line and in the center 
of the face of the gear. If the pitch is comparatively large in 
proportion to the diameter of the pitch circle, the angle will be con¬ 
siderably less at the bottom of the tooth than on the pitch line, and 
considerably greater at the points of the teeth. 

The simplest form of spiral gears is shown in Fig. 275, in which 
the shafts are parallel and the teeth of both gears are cut at an angle 



224 






































MACHINE SHOP WORK 


213 


of 30 degrees to their axes. This angle is not arbitrary, as any angle 
that permits the teeth to engage properly is admissible. It should not 
exceed 45 degrees. The two gears may have relatively any number 
of teeth, the same as spur gears. Gears of this form are frequently 
called helical, in consequence of their spiral form of teeth resembling 
the helix. This is the customary angle for such gears. Their action 
is similar to that of ordinary spur gears; but in consequence of the 
progressive engagement of the teeth, they will run with less noise 



Fig. 276. Spiral Gears Whose Shafts Are at Right Angles 


and shock, even when running at high speeds or when transmitting 
heavy loads. 

Fig. 276 represents a pair of spiral gears whose shafts are at 
right angles to each other, and in which gear A has 8 teeth and the 
gear B has 16 teeth. Gear A is the driver; and from the fact that it 
has but one-half the number of teeth of the gear B, its speed must 
be twice as great. The angle of the teeth of gear A is 26 degrees 
40 minutes. As the shafts stand at an angle of 90 degrees, we 
subtract the angle of the teeth of the gear A from 90 to obtain the 
angle of the teeth of the gear B, giving 63 degrees 20 minutes. 
The sum of the two angles equals the angle of the two shafts. That 
spiral gearing and worm gearing are closely allied is evident from 


225 

























214 


MACHINE SHOP WORK 


this example. In analyzing the action of these devices, this fact 
should not be forgotten. 

The necessary calculations for designing a pair of spiral gears 
may be illustrated by the following example: The gears are to be 4 
and 16 inches diameter of pitch circle, and the shafts are parallel. 
The larger will have a lead of 96 inches; therefore the smaller will 
have a lead in the same ratio as the diameters, or 24 inches. Taking 
the large gear, 16X3.1416 = 50.2656 circumference, which, divided by 
the lead (96), gives .5235. Consulting a table of natural tangents, 
we find that this amount represents an angle of 27 degrees 40 min¬ 
utes. The angle of the smaller gear will be the same. 

If shafts are at other than right angles, this condition will 
change the angles of the teeth of spiral gears; and when the pitch 
diameters are alike and the numbers of teeth different, the angles 
will be different. 

It is customary to use racks in connection with spiral gears, the 
gear being of comparatively short lead. This device is practically 
the screw and nut, the spiral gear acting as the screw and the rack as 
the nut. In designing racks for this purpose the teeth may be at 
right angles to the line of movement or at any angle between this 
position and 45 degrees. The shaft of the spiral gear used with a 
rack may be at any angle from parallel to the line of motion to 45 
degrees. Angles of 35 degrees or less -will produce better results 
under usual conditions. The pitch of the spiral, the number of 
teeth, and the angle of the shaft will govern the angle of the teeth 
of the rack. The teeth of the rack may be of concave form, similar 
to those of the worm gear if a large area of contact is required for 
heavy work. Otherwise they are usually cut in a straight line. 
The form of the teeth should be with straight lines for the side of 
the teeth, inclined 14§ degrees. 

GEAR CUTTING PROCESSES 

Two general processes are used for cutting the teeth of gears: 
milling and planing. Either of these processes may be used for 
cutting the teeth of spur gears, bevel gears, internal gears, racks, 
etc., but they are not equally adapted for spiral gears or worm gears. 

Milling Process. The first process, milling with a properly 
formed revolving cutter, as in ordinary milling machine work, is 


226 


MACHINE SHOP WORK 


215 


applicable not only to the work mentioned above, but also to the 
cutting of spiral gears and a portion of the work upon worm gears. 
The cutter must be shaped exactly to the form of the space between 
the teeth of the gear to be cut. It must revolve at a speed suitable 
to the kind of metal to be cut, and must be supported by a spindle 
of ample dimensions properly supported in well-fitting journal 
boxes, set in housings of such dimensions and weight as to insure 
rigidity and the elimination of vibration. The work to be cut must 
be properly mounted so as to avoid vibration as much as possible, 
and be provided with feeding mechanism by which a rate of feed 
may be produced according to the speed of the cutter and the kind 
of metal to be cut. 

For ordinary uses this process produces satisfactory results upon 
spur gears, internal gears, and racks. While it is used also for much 
bevel gear work and answers the requirements of ordinary work, 
there are conditions in the form of teeth of bevel gears that do not 
exist in that of spur gears. It has been previously explained that the 
dimensions of the tooth parts of a bevel gear are measured at 
the outer end, or at the largest part of the tooth, while the lines of the 
tooth are radial, meeting at the apex of the cone base, from which 
the gear takes its form. It may therefore be readily understood 
that it is quite impossible to form a revolving cutter so as to cut to 
the correct theoretical dimensions of the tooth through its entire 
length. It is the practice to form the contour of the cutter so that 
it is a compromise between the correct forms of the two ends of the 
teeth, but rather closer to the form at the outer or larger end, 
the form being practically correct at a point one-third of the face of the 
tooth from its outer end. As a rule, the width of face of a bevel 
gear should not be over five times the thickness of the teeth at the 
outer end. It is usually considerably less. If the face is too wide, 
the inner ends of the teeth will be cut away too much as the width 
of the cut is uniform from one end to the other; and this results in 
thin and useless teeth for a considerable part of their length 
from the inner end, as there is no contact with or bearing upon 
the teeth of the engaging gear at this point. For this reason, 
resort is had to filing the faces of the teeth at the large end, 
after the gears have been run together so as to show by the marks 
thus produced. 


227 


216 


MACHINE SHOP WORK 


Planing Process. First Method . The second process, that of 
planing the forms of the teeth, is accomplished by three methods. 
One is to form a planing tool to the exact contour of the space between 
the teeth, and by successive strokes of any machine having a recip¬ 
rocating ram to carry the tool, some fixture for holding the gear 
blank, and a device for indexing the tooth spaces. This work is 
frequently done on a shaper and sometimes on a planer. This 
method produces a cut with parallel sides the same as a revolving 
cutter, and the depth of the cut may be varied at the two ends so 
as to be adaptable to bevel gear work although producing work that 
is no more theoretically correct than that of the revolving cutter. 
This device may be used upon spur gears, internal gears, racks, etc., 


with fairly good effect, 
but is a comparatively 
slow process. It may, 
however, be sometimes 
used where a milling 
machine or ordinary 
gear cutter cannot, as 
in cutting the teeth of 
internal gears. 



Blank. 


Second Method. The 
second method, of plan- 


Fig. 277. Planing Gear Teeth 


ing gear teeth—which has proven an important device for forming 
the teeth of spur gears, internal gears, and racks—operates by means 
of a circular cutter upon which the teeth are formed similar to the 
teeth of the gear itself. This is the system used in the Fellows 
gear shaper. The action of the cutter is shown in Fig. 277. The 
gear blank is mounted on a proper spindle, and the machine started, 
the cutter reciprocating on its center line and parallel to its axis. 
The cutter is then fed toward the blank, and cuts its way to the 
proper depth. At this point, both the cutter and the blank begin 
to rotate in the directions indicated by the arrows, the cutter main¬ 
taining its reciprocating motion. This rotation of the cutter and 
the blank is obtained by separate and external mechanism, which 
insures that the movement shall be the same as though the cutter 
and the blank were two complete gears in correct mesh. The com¬ 
bined result of rotary and reciprocating motions is that the cutter 


228 



MACHINE SHOP WORK 


217 


teeth generate conjugate teeth in the blank, which mesh correctly 
with the cutter teeth and with one another. Any two gears of the 
same pitch cut with this cutter will mesh correctly together. 

Third Method . A third method of planing gear teeth, and one 
of very great importance, particularly in forming the teeth of bevel 
gears, is used by various gear-cutting machine builders. In some 
cases the tool slide travels upon a carriage whereof one end is pivoted 
directly under the apex of the base cone, and its opposite or outer 
end is properly guided to the exact contour of the tooth, which is 
formed by a tool having a single cutting edge with a narrow and 
somewhat rounded cutting point. In other cases the tool slide is in 
a fixed plane, while the arbor upon which the gear blank is mounted 
is journaled in a portion of the 
machine so constructed as to give 
the necessary adjustment and 
movements to the gear blank. 

These planing processes will be 
more particularly noticed later in 
describing the various types of 
gear-cutting machines. 

Hobbing Gears. In forming 
the teeth of worm gears, the greater 

part of the space IS cut out by a Fig. 278 . Hob for Forming Teeth of 
stocking cutter or roughing cutter, 

which is adjusted at a proper angle, according to the pitch of the 
worm which the worm gear is to fit, and gradually sunk into the face 
of the worm-gear blank so as to form the spaces between the teeth. 
This revolving cutter will not produce the correct form for the teeth, 
as they must fit the sides of the worm thread. Recourse is therefore 
had to a cutter called a hob, which is shown in Fig. 278. This cutter 
is in effect a worm, across the threads of which are formed deep 
grooves, thereby producing cutting faces as shown in the engraving. 
Each of the teeth shown is relieved, or backed off, so that when the 
faces of the teeth become dulled by use and are ground, the accurate 
form of the teeth is not changed. This hob is mounted in the exact 
position that the worm is to take with reference to the worm gear, 
except that the centers of the spindle carrying the hob, and the arbor 
carrying the worm gear, are slightly farther apart, and so arranged 



229 


218 


MACHINE SHOP WORK 


as to be brought to the exact distance apart, as the hob shapes the 
teeth of the worm gear. This operation, called hobbing, is per¬ 
formed by the rotation of the hob, which, acting as a screw and 
producing the rotation of the worm gear, forms the teeth by its 
cutting action. In some cases the worm gear is positively rotated 
by suitable gearing. Previous gashing is then unnecessary. 

In Fig. 279 is shown the usual form of a rotating cutter for pro¬ 
ducing the involute form of gear teeth. The teeth of these cutters 

are relieved, or backed off, so that 
their form is not changed when 
ground upon the face after they have 
become dulled by use. 

Tools for Testing Gear Teeth, 
To ascertain if the teeth of a gear 
are being cut properly, the gear- 
tooth caliper shown in Fig. 280 is 
used. This is for measuring the dis¬ 
tance from the top of the teeth to the 
pitch line, and the thickness of the 
teeth at the pitch line. It will meas¬ 
ure all teeth from 2 to 20 diametral 
pitch, and is provided with vernier 
scales in both directions so that it 
can be very accurately adjusted to 
the required dimensions as given in 
Table X. 

Fixed gages are frequently used 
instead of the gear-tooth caliper. Thus, for the depth of the teeth, 
a sheet-metal gage of the form shown in Fig. 281 is provided. A 
gage for the width of the teeth is shown in Fig. 282. There must 
be separate gages for each different pitch, each of which is stamped 
with a figure indicating the pitch for which it is to be used. 

General Conditions of Practical Gear Cutting. Before describ¬ 
ing the various types of gear-cutting machines and the methods by 
which each performs its work, attention is directed to some of the 
general conditions in the practical use of gear-cutting machines of 
any type. 

When rotating cutters are used, they are mounted upon the 



230 



















MACHINE SHOP WORK 


219 


spindle and secured in place in the same manner as ordinary milling- 
machine cutters—namely, located in proper position by clamp collars 



Fig. 280. Gear-Tooth Caliper in Use 


on each side, held in place by a nut. Care should be taken to see 
that they run true. If not, there is liable to be dirt or chips between 
the collars and shoulders of the arbor or the cutter; and they should 
be removed, carefully 
cleaned, and replaced. 

If still out of true, the 
arbor may be sprung, 
and it should be cor¬ 
rected before any work 
is done. The cutters 
should be sharp; other¬ 
wise much heat and 
friction will be caused, 
and poor and inefficient 
work will result. 

The gear blank is 
usually mounted upon 
a work arbor fitting in a taper-reamed hole in the spindle, and 
sometimes reaches entirely through the spindle, being confined in 
position by a nut in its rear end. These arbors are of different 



Fig. 281. Sheet-Metal Gage for Measuring Depth of Teeth 


231 









































220 


MACHINE SHOP WORK 


diameters so as to fit all the regular sizes of the bore of the gear 
blanks. The gear blank is adjusted to its proper place on the arbor 
by loose collars if necessary, and confined by a nut which must be 
screwed up very tightly so as to prevent the blank from moving 
on the arbor during the process of the cutting. 

Upon the cutter shown in Fig. 279 is a line A , exactly in the 
center of the tooth. The position of the cutter and the work arbor 
carrying the gear blank must be so adjusted with relation to each 
other that this line will exactly coincide with the axis of the arbor. 
To effect this, in machines in which the work arbor is vertical, it is 
brought under the cutter and accurately adjusted; then the arbor 

and its carriage are moved 
to the proper position to be¬ 
gin cutting the teeth. On some 
machines, special provision is 
made for centering the cutter. 

The proper change gears 
or such similar devices as the 
machine is provided with are 
then arranged for the spacing 
or indexing of the blank. The 
design of this device may vary 
in different machines, but the 
device usually consists of or¬ 
dinary change gears, which are selected and applied according to 
a table furnished with the machine, which table gives the required 
gears for all the usual numbers of teeth to be cut. The machine is 
started, and the work brought to the cutter so as to mark it plainly, 
when it is withdrawn and the machine stopped. The indexing device 
is now operated, step by step, through one entire revolution of the 
gear blank, back to the mark made by the cutter. The work is 
now brought up to the cutter to ascertain if it exactly coincides 
with the mark made. If so, the cutter may be set to the proper 
depth by advancing it to a point considerably less than the whole 
depth, and cutting down slightly past the center of the cutter; 
then moving the cutter, in the line of its feed, out of the cut, and 
measuring the depth. The work is now slightly advanced and 
the cut deepened; and so on, until the proper depth is reached. 



232 










MACHINE SHOP WORK 


221 


On some machines an index is provided on the adjusting screw, 
enabling the work to be brought up to the cutter so as to barely 
touch it; and then, by reading the index, the entire depth is adjusted 
at once and with certainty. 

When gears of very coarse pitch—as 2\ pitch and larger made of 
cast iron, and 5 pitch and larger made of steel—are to be cut, it is 
customary to use first a roughing or stocking cutter which removes 
two-thirds or more of the metal, after which the finishing cutter, 
shown in Fig. 279, is used to finish the work. A roughing cutter 
usually has inclined, straight, or stepped sides, no attempt being 
made to follow the contour of the finished tooth. 

Speed of Cutters. On gear work the speed of cutters will be 
slightly less than that of the ordinary milling cutters, as the cutting 
surface is not only over the points of the cutting teeth, but upon 
both sides. Hence the speed will more nearly approach the proper 
speed for the formed cutters of the milling machine. The variations 
of speed for the different kinds of material will be the same as for 
milling-machine cutters. 

Feed. The proper feed for gear cutting will be the same as for 
milling-machine cutters (or in some cases slightly less), on the same 
material, for cast iron usually about inch per revolution. 

Cutting Spiral Gears. In cutting spiral gears the universal 
milling machine is generally used, as it is provided with proper 
devices for rotating the gear blank at the same time that it is fed 
toward the cutter. The machine is provided with an indexing 
mechanism, and also with change gears by which any length of lead 
of the spiral may be obtained. In all cases of spiral gear cutting, 
the milling-machine table must be set at an angle, as shown in 
Fig. 276, the center of the cutter being directly above the point of 
intersection of the axes of the arbor carrying the gear blank and that 
upon which the cutter is mounted. 

The preliminary cutting or gashing of worm gears is frequently 
done on a universal milling machine, on account of its adaptability 
to all kinds of angular work and to making feeds in all directions. 

Lubrication of Cutters. In gear cutting, the lubrication of 
cutters is governed by the same conditions and requirements as in 
ordinary milling-machine work, and is governed by the material to 
be cut. 


233 


222 


MACHINE SHOP WORK 


TYPES OF GEAR=CUTTING MACHINES 
To familiarize the student with the special features of different 
types of gear-cutting machines, illustrations and descriptions are 
given of the machines made by some of the more prominent builders. 

Whiton Gear=Cutting Machine. In Fig. 283 is shown the 
Whiton automatic gear-cutting machine. The cutter is carried by 



Fig. 2S3. Automatic Gear-Cutting Machine 
Courtesy of D. E. Whiton Machine Company, New London, Connecticut 


the spindle A, which is journaled in a saddle B, sliding upon the 
swinging carriage C and capable of adjustment at any angle neces¬ 
sary to cut bevel gears. The machine is shown arranged for cutting 
spur gears. The cutter arbor A is driven by the pulley D at the 
back of the machine, acting through a system of gears not shown. 
The blank to be cut is held on an arbor fitted into the vertical spindle 
E t and its upper end supported by a center in the arm, adjustably 


234 



MACHINE SHOP WORK 


223 


clamped to the column G. The traversing screw II, has a graduated 
dial. A gage is provided for centering the cutter; and graduated 
stops provide micrometer adjustments for setting over the cutter 
in bevel gear cutting, and for setting over the blank. At J are the 
change gears of the indexing mechanism. 

Brown and Sharpe Gear=Cutting Machine. Fig. 284 repre¬ 
sents a Brown and Sharpe gear-cutting machine. The gear blank is 



Fig. 284. Number 6 Gear-Cutting Machine 
Courtesy of Brown and Sharpe Manufacturing Company, Providence, Rhode Island 


carried on an arbor fitted to the horizontal spindle A y and supported 
by the outer supporting bracket B. The indexing mechanism is in 
the rear of the indexing wheel C. The cutter is carried by the cutter 
spindle D f mounted in the traveling carriage E. In smaller machines 
the base upon which this carriage slides is pivoted so as to be 
set at any required angle for cutting bevel gears. The machine is 


235 




224 


MACHINE SHOP WORK 



entirely automatic in its action. It has an attachment for cutting 
internal gears. 

Automatic Gear=Cutting Machine. The automatic gear-cutting 
machine built by Gould and Eberhardt is shown in Fig. 285. It is 
of the same type as that built by Brown and Sharpe and possesses 
some excellent features. The gear blank and cutter are mounted in 
a similar manner, and the adjustments are made at much the same 
points. It is furnished with attachments for hobbing worm gears 


Fig. 285. “New Type” Gear-Cutting Machine Entirely Automatic for Cutting Spur Gears Only 
Courtesy of Gould and Eberhardt , Newark , New Jersey 

and for cutting racks and internal gears. The one shown is not 
adapted for cutting bevel gears. 

Becker Gear=Cutting Machine. The Becker Milling Company 
gear-cutting machine, shown in Fig. 286 is of the milling-machine 
type, designed by Amos H. Brainard, a builder of milling machines. 
The gear blank is mounted upon an arbor fitting a taper hole in 
the work spindle A or fixed upon an arbor and mounted on centers. 
The cutter is mounted upon a cutter arbor B, journaled in a sliding 
saddle C whose support D is pivoted to the machine knee so as to be 


236 









MACHINE SHOP WORK 


225 


adjustable to any angle required for cutting bevel gears as well as 
spur gears. The machine is entirely automatic in its action. 

Bench Gear=Cutting Machine,, Fig. 287 shows a bench gear¬ 
cutting machine built by the Sloan and Chase Manufacturing Com¬ 
pany. It is intended for small gears only, and will not cut a gear 
larger than 3§ inches in diameter. The same company build large 
machines, some of the Brainardtype. The machine shown carries the 



Fig. 286. Gear Cutter 

Courtesy of Becker Milling Machine Company, Hyde Park, Massachusetts 

gear blank on the spindle A, and the cutter on the spindle B. The 
indexing mechanism is at C, and the machine is entirely automatic. 

Fellows Gear Shaper. The Fellows gear shaper, shown in 
Fig. 288, is a distinct type in construction and action, the peculiar 
form of cutter used being shown in Fig. 277. The gear blank is 
mounted on the vertical work spindle A, which has on its lower end 
and within the casing B an indexing worm gear operated by the 
change gears at C, These are driven from the cone pulley D by 
means of the vertical shaft E , by a very gradual but continuous 


237 






226 


MACHINE SHOP WORK 


motion as the vertically reciprocating cutter F forms the teeth on 
the blank, gradually rotating in unison with the rotation of the blank. 
The reciprocating movement of the ram carrying the cutter is pro¬ 
duced by suitable mechanism within the casing II operated by the 
shaft G. The machine is automatic in its action, and cuts spur gears 
and internal gears. A modified form machine is adapted to cutting 
the teeth of racks. The cutting action is that of planing. 

Gleason Gear Planer. In Fig. 289 is shown the Gleason gear 
planer which is an excellently designed machine for planing gear 



teeth with a single tool having a narrow, rounded cutting point. 
The gear blank A is mounted on a horizontal spindle having at its 
rear end suitable automatic indexing mechanism B. The tool C is 
carried in a reciprocating tool block D, which travels upon a swing¬ 
ing carriage pivoted at E directly under the apex of the base cone of 
the gear blank. The exact curve and direction of its feed are con¬ 
trolled by one of the formers F , G, H, mounted upon the triangular 
former carrier J , which may be rotated so as to bring either former 
up to its operative position, forming a rest and guide for the friction 
roller K on the outer end of the swinging carriage. Of the three 


238 



























































MACHINE SHOP WORK 


227 


formers, F is used for a roughing cut, and the other two for the upper 
and under sides of the tooth. Being placed at a considerable distance 
from the pivot upon which the carriage swings, they are made many 
times larger than the tooth, and great accuracy of form is thereby 
secured. The roughing cut is frequently made with a rotating cutter 



Fig. 288. Gear Shaper 

Courtesy of Fellows Gear Shaper Company, Springfield, Vermont 


on an ordinary gear cutting machine. Modifications of this machine 
are built specially for cutting spur gears upon the same principle. 

Bilgram Gear=Planing Machine. The Bilgram gear-planing 
machine, shown in Fig. 290, operates upon a principle similar to that 
of the machine just described, but with this important difference. 
In the Gleason machine the tool is caused to move so as to trace the 
exact contour of the side of the gear tooth, in addition to its recipro- 


239 








228 


MACHINE SHOP WORK 


eating movement for cutting. In the Bilgram machine, on the other 
hand, the tool has only a reciprocating motion, while the gear blank 



Fig. 289. Gear Planer 

Courtesy of Gleason Tool Company, Rochester, New York 



and its supporting mechanism are given the rolling motion similar 
to that imparted by one rotating gear to another, or that of a rolling 


240 



























MACHINE SHOP WORK 


229 


cone. To accomplish this, the axis must in the first place be moved 
in the manner of a conical pendulum. Therefore the bearing of the 
arbor which carries the blank is secured in an inclined position 
between two uprights to a semicircular horizontal plate, which can be 
oscillated on a vertical axis passing through the apex of the base cone 
of the blank. To complete the rolling action, the arbor must in the 
second place receive simultaneously the proper rotation; and this 
effect is produced in the machine by having a portion of a cone 
(corresponding with the pitch cone of the blank) attached to the 
arbor, and held by two flexible steel bands stretched in opposite 
directions, one end being attached to the cone and the other to a 
fixed part of the mechanism, thus preventing this cone from making 
any but a rolling motion when the arbor receives the conical swinging 
motion. In the engraving A is the blank to be cut; B the ram 
carrying the cutting tool; and C the indexing and rolling mechanism. 

TURRET LATHES 

The turret lathe, as we know it today, is a comparatively modern 
machine, and was developed from an ordinary engine lathe by the 
addition of revolving tool-holding devices called turrets. 

The turret w r as at first made of circular form, and rotated upon 
a vertical pivot wdiich had a binding nut whereby it could be held in 
any desired position. The circumference of the circular turret was 
drilled and reamed for four tools projecting horizontally from it at 
angles of 90 degrees wdth each other. Later the number of tool holes 
was increased to six, and the turret was frequently made of hex¬ 
agonal form. 

The turret was at first located upon a lathe carriage in place of 
the tool block, and properly set in line wdth the lathe center by means 
of the cross-feed screw. The lateral feed, upon which the device 
depends for its action, was obtained by the operation of the feeding 
mechanism in the apron attached to the carriage. 

The object sought to be accomplished by the addition of this 
device to the lathe w r as that of carrying various drilling, reaming, 
counterboring, and similar tools by wdiich several operations could be 
performed upon a piece of work without removing it from the chuck, 
or wdthout any further change of tools than that of revolving the 
turret. The tools, when once adjusted, required no further altera- 


230 


MACHINE SHOP WORK 


tion as the several pieces of work were completed and removed from 
the chuck, and other pieces substituted for a like series of operations. 
By this means the work could be performed much more rapidly, the 
value of the machine being correspondingly increased. 

Fig. 291 shows the original form of the turret A, supported upon 
the sliding block B. The turret is pivoted upon the vertical stud C, 
and secured in any desired position by the nut. A later development 
provided means for locating it positively in as many positions as 



there were holes for tools. This turret is drilled for four tools, three 
of which are shown lat EEE secured by the set screws eee. 

As the value of the turret mechanism came to be generally appre¬ 
ciated, it was still further developed by the addition to the number of 
tools that it would carry; by a ratchet arrangement for revolving it; 
by an index plate for holding it in any desired position; and by vari¬ 
ous other improvements that will presently be referred to. 

These developments soon carried it beyond the scope of the 
engine lathe, and special lathes were designed in which the improved 
turret was the principal feature. These are the turret lathes 
proper, as we find them built today. 

Classification of Turret Lathes. To obtain a comprehensive 
view of the various forms of turret lathes, including engine lathes so 


242 
































MACHINE SHOP WORK 


231 


modified as to adapt them to turret-lathe work, they may be divided 
into five classes as follows: 

(1) Engine lathes adapted to serve as turret lathes by having a hand- 
revolved turret mounted upon the carriage in place of the usual tool-block or 
compound rest. 

(2) Engine lathes adapted to serve as turret lathes by having a hand- 
revolved turret mounted upon a laterally moving slide, supported upon a shoe 
or saddle fitting the V’s of the bed. 

(3) The turret lathe proper, specially designed and built as such, with 
a turret revolved and fed by hand, supported by and pivoted upon a slide, 
which is in turn supported by a shoe or saddle fitted to the V’s of the bed. 

(4) A turret lathe designed and built in a similar manner to that last 
described, and in which there is a power feed for the cuts. It is so arranged 
that the turret is revolved automatically. This lathe is frequently called a 
semi-automatic turret lathe. 

(5) A complete automatic turret lathe having a power feed for the cuts; 
a quick return of the turret slide, operated by power; with the turret automatically 
revolved at the end of its run. 

The lathes described in the third, fourth, and fifth classes are 
usually provided with a carriage called a cross-slide, carrying one 
cutting tool in front and frequently another tool at the back, inverted 
so as to cut without reversing the direction of revolution of the work. 

A very useful modification of the type described in the third class 
is called the monitor lathe, probably from the fancied resemblance of 
its turret to the turret of the type of warship called a “monitor”. In 
this lathe the slide upon which the turret is supported and pivoted 
is moved back and forth by means of a horizontal hand lever, and 
is therefore very rapid in its operation. From the fact that this con¬ 
stitutes a rapid hand feed for the turret, this type is adapted for light 
work or work upon soft metals. For this class of work it is a very 
rapid and efficient machine. Fig. 292 show T s one of these machines. 
The lever A is for operating the turret slide B, carrying the turret 
(7, which was first revolved by hand but later by a ratchet device 
located in its base and actuated by a pawl during the latter portion 
of the movement of the slide in withdrawing the cutting tools from 
the work. The lever D is for operating the cross-slide E, carrying a 
cutting-off tool and frequently a forming tool also. 

In a general way it may be said that the turret lathe is one of the 
most useful and efficient machines in the shop for the production of 
parts in large (and often in moderate) quantities usually known as 
repetition work, which can be finished by the operations of turning. 


243 


232 


MACHINE SHOP WORK 


facing, boring, reaming, counterboring, or any similar circular work, 
the machine being equipped with suitable tools for the work under¬ 
taken. 

This machine is practically identical with that frequently known 
as a hand screw machine, which has the wire-feed attachment for 
feeding bars of stock through the main spindle. It is used for mak¬ 
ing not only screws, but many small cylindrical parts, particularly 



when the quantities of one kind are not of sufficient number to make 
it economical to set up the automatic screw machine for their manu¬ 
facture. The other machine which is the only successful rival of the 
turret lathe and the hand machine, is of the same family, but know T n 
as the “automatic screw machine”, which will be illustrated and 
described later on. 

An engine lathe equipped as described in class 1 is shown in 
Fig. 293. In this particular machine, the turret is of hexagonal 


244 












































MACHINE SHOP WORK 


233 


form. In the earlier machines it was usually cylindrical. It is 
arranged to be revolved by hand, and is released or held in place as 
desired by a plunger operated by the lever A and engaging in slots 
in the periphery of a circular plate attached to the base of the turret. 
The transverse position of the turret is adjusted by the cross-feed 
screw B; and the lateral movement or cutting feed is by the crank 
C y or by the power lateral feed of the lathe. The turret is pivoted 
to the shoe D, which is quite similar to the one shown in Fig. 291, 
and fits on the dovetail of the lathe carriage after the removal of the 



Fig. 2D3. Engine Lathe with Hand-Revolved Turret on Carriage in Place of Tool-Block 


regular compound rest or tool-block. In all other respects this 
machine is a regular engine lathe. 

Fig. 294 shows the machine referred to in class 2. In this case 
the tailstock of the engine lathe is removed, and replaced by a base 
A similarly attached, which supports the turret slide B y upon which 
is pivoted the turret C. The base A is fixed at any desired point on 
the lathe bed. The turret slide B is operated by the pilot wheel D, 
and limited in its forward movement by the adjusting screw E. 
Frequently there are several of these screws in a sliding, swinging, or 
rotating stop-holder, by which device an adjustable stop may be pro¬ 
vided for each tool in the turret. The regular compound rest F is 
retained in its place, and may be used to carry forming or cutting-off 


245 



234 


MACHINE SHOP WORK 



246 


Fig. 294. Engine Lathe with Hand-Revolved Turret Mounted on Latterally Moving Slide 



















MACHINE SHOP WORK 


235 



tools. The lathe proper may be any form of an engine lathe. Nearly 
all manufacturers of engine lathes now furnish turrets to fit either 
upon the carriage or upon the V’s of the bed, for the purpose of doing 
these classes of work. 

The machine specified in class 3 is shown in Fig. 295. It is 
designed and built as a turret lathe. The base A, turret slide B, 
turret C, and pilot wheel D are constructed and operate as in the last 
example. The turret slide A is provided with an adjustable multiple- 
stop screw E, by which the length of cut of each individual tool in the 


Fig. 295. Turret Lathe, Hand-Revolved and Hand-Fed 
Courtesy of Pratt and Whitney Company, Hartford, Connecticut 

turret is limited. A simple form of cross-slide takes the place of the 
carriage on the engine lathe. It is adjustable to any point on the bed. 
It carries two tool-blocks which may be adjusted in relation to each 
other by the hand-wheel G . The entire top slide carrying the two 
tool-posts HII is operated transversely by means of the lever J . By 
this device, a cutting-off tool may be carried in one tool-post, and a 
forming tool in the other. This machine is built in various sizes. 
It is equipped with chucks for taking round and hexagonal rods of 
different diameters; and with much larger chucks for holding castings 
and drop forgings which are to be bored, reamed, turned, faced, or 


247 










236 


MACHINE SHOP WORK 


formed. It is also provided with what is called a wire feed, by means 
of which long bars are automatically passed entirely through the main 
spindle and chuck. This device will be shown and explained in con¬ 
nection with Screw Machines. Provision is made for lubricating 
the tools by a stream of oil or other lubricant, contained in the tank 
K beneath the machine, whence it is drawn by a small rotary pump 
(not shown in the engraving) and forced up through the piping L, 
from which it falls upon the cutting tools. 

In Fig. 296 is shown a turret lathe, fulfilling the requirements 
stated in class 4. The turret is mounted in substantially the same 
manner as in the last example, and is automatically revolved at the 



Fig. 296. Semi-Automatic Turret Lathe. Turret ia Automatically Revolved 
at End of Each Stroke 

Courtesy of Bullard Machine Tool Company, Bridgeport, Connecticut 


end of the return stroke. It is hexagonal in form, and the six faces 
are not only drilled and reamed for holding tools, but the faces are 
accurately surfaced, and are drilled and tapped so that large tools 
and special devices may be bolted to them when necessary or desir¬ 
able. An elaborate and useful system of adjustable stops controls 
and limits the travel of individual turret tools. The cross-slide is 
designed more upon the lines of an engine lathe carriage, and has 
attached to it an apron which carries the necessary gearing for feed¬ 
ing purposes. The carriage carries tool-posts for one front and two 
back tools. The movement of the carriage on the cuts is limited by 
pivoted, adjustable stops for each of the three tools. There is a 
system of piping for the lubrication of the turret tools, and another 


248 






MACHINE SHOP WORK 


237 


for the three carriage tools. The headstock is triple-geared so as to 
give various gear as well as belt speeds and a powerful drive for 
heavy work. These changes of the gear speeds are made by levers, 
without stopping the machine. The main spindle is hollow so as to 



take bars through it, and the chucks are adapted to take round, 
hexagonal, or square bars. There is a taper attachment at the back 
of the carriage, by means of which tapered as well as straight work 
can be turned by the carriage tools. 

A very complete turret lathe is shown in Fig. 297, as an example 


249 









238 • 


MACHINE SHOP WORK 


of class 5. The turret is mounted upon a carriage fitted to the V s 
of the bed, and provided with an apron carrying the feeding mech¬ 
anism. The turret is not set upon a horizontal support and pivoted 
on a vertical stud, as in the former examples, but it is inclined toward 
the back of the machine for the purpose of elevating the long turret 
tools out of the way of the operator. The turret is hexagonal, and 
the faces drilled and reamed for holding cylindrical shanked tools, 
and also accurately faced, drilled, and tapped for bolting on large and 
heavy special tools and devices. The turret is revolved automati¬ 
cally, and the cutting movement is controlled and limited by indi¬ 
vidual adjustable stops for each turret tool. The lateral movement 



Fig. 298. “Prentice” High-Speed Turret Lathe 
Courtesy of Reed-Prentice Company, Worcester, Massachusetts 


of the turret is produced by a lead screw of very sharp pitch, so that 
the return stroke is not only automatic but rapid. Upon a heavy 
carriage, designed upon the lines of a heavy engine lathe carriage, is 
mounted a revolving tool-post adapted to carry four tools for cutting- 
off, forming, turning, etc. A taper-turning attachment is located at the 
rear of the carriage, whereby tapered work may be as readily turned 
as straight work. The lateral movement of the carriage is con¬ 
trolled and limited by four adjustable stops at the left, thus provid¬ 
ing individual stops for the tool-post tools. Stops are also provided 
for their transverse cuts. A system of piping is provided, whereby 
all tools may be lubricated by oil or other lubricant, under pressure 


250 










MACHINE SHOP WORK 


239 


from a rotary oil-pump. This form of lathe is built very substan- 
tially, and is intended for the machining of large and heavy castings. 
For this purpose the turret as well as the carriage is equipped with 
long and heavy tools, some of which will be illustrated and described 
later on. The headstock of this lathe is very large and substantially 
built, and is triple-geared so as to give it great driving power for 
heavy work. It is driven by an electric motor, the rheostat for 
which is seen at the extreme left of the engraving, near the floor. 
In Fig. 298 is shown an automatic turret lathe built by the Reed- 
Prentice Company of Worcester, Massachusetts. 

Fig. 299 shows what is known as the flat turret lathe, so called 
from the design of the turret. In this case the tools are not placed 



Fig. 299. Flat Turret Lathe, with Special Tools Bolted to Top of Flat Plate 
Courtesy of Jones and Lamson, Springfield, Vermont 


in tool holes in the outside of the turret nor bolted to the faces of it. 
On the contrary, they are bolted down to the upper surface of a 
horizontal, circular plate. It is a radical and most successful inno¬ 
vation in the designing of a turret lathe, and requires tools and fixtures 
specially designed for its use. 

In other examples w r e have what is called the hollow hexagonal 
turret, wdiich, instead of being made solid as in Fig. 293 and numerous 
other examples, consists of walls of sufficient thickness to properly 
support the tool-holders and the tools bolted to it. 

Turret=Lathe Tools. A great variety of tools are used in the 
turret lathe, and for an infinite number of uses, as the different forms 
of pieces to be machined are of a never-ending variety of shapes which 


251 







240 


MACHINE SHOP WORK 


almost defies any attempt at analysis or classification. It is possible, 
however, in a general way, to separate these tools according to the 
work which they are designed to do, as follows: 

(1) For the Turret: Centering tools, drills, reamers, counterbores. 
For the Cross-Slide: Cutting-off tools and plain forming tools, as for fin¬ 
ishing the end of the bar after a machined piece is cut off, cutting a groove in 
the work before it is cut off, etc. 

(2) For the Turret: Plain box tools containing a turning tool and a 
back rest, both adjustable to different diameters) taps and threading dies and 
holders for the same; forming tools that may be run on the end of a cylindrical 
piece of work. For the Cross-Slide: In addition to the cutting-tools, horizon¬ 
tally moving and vertically moving forming tools. (Occasionally these 
tools may be so made as to move in an inclined direction.) 

(3) For the Turret: Box tools carrying several turning or forming 
tools, or both, with the necessary back rests, bushings, etc. For the Cross- 



Slide: Facing tools; multiple tool-holdfcrs, carrying, turning, cutting-off, and 
forming tools, and special tool-posts. 

(4) This class includes a large number of special tools and fixtures for use 
in both the turret and cross-slide, by which a great variety of work of all sizes 
and forms is successfully machined. 

Tools for the Turret. Drills, reamers, boring bars, counter¬ 
bores, etc., may have shanks formed upon them, or may fit in collets 
fitted to the tool-holes in the turret, or in plain drill-holders. A split 
collet is shown in Fig. 300; and a plain drill-holder, in Fig. 301. 

Taps and dies may be held in the releasing holder shown in 
Fig. 302. The shell A is fitted to the tool-hole in the turret, through 
which the shank of the holder B passes and is permitted to revolve 
freely, except when the two are locked together by the pins CC when 
pressure is applied against the face of the die-holder, or by the pin 
D when pressure is exerted in the opposite direction. In the medium 
position, both pins are inoperative. This permits right- and left- 
hand dies to be used, the machine being reversed at the proper 
moment. 


252 











MACHINE SHOP WORK 


241 



Fig. 302. Releasing Holder 


Fig. 303 shows a 
simple form of box tool, 
in which A is the shank 
entering the tool-hole in 
the turret; BB are the 
cutting tools, adjusted 
by the screws bb; and CC 
are the jaws of the back¬ 
rest device adjusted to 
the diameter of the 
turned portion of the 
work by the screws cc. 

Of the two tools, the 
leading one is for rough¬ 
ing, and the other for 
finishing. 

In the box tool 
shown in Fig. 304, the 
two tools BB are adjust¬ 
able with relation to each 
other; hence two shoul¬ 
ders may be turned upon 
a piece of work simulta¬ 
neously, at a required 
distance apart. One box 
tool may make the 
roughing cuts, and in the 
next tool-hole may be a 
similar box tool with its 
tools set to make the 
finishing cuts. The back¬ 
rest jaw C is also adjust¬ 
able, so as to keep it di¬ 
rectly back of the lead¬ 
ing tool. If the box tool 
is so constructed as to 
have the tools BB at a considerable distance apart, two back-rest 
jaws may be necessary, being set in the slots shown. 



Fig. 304. Double Box Tool 


253 
































242 


MACHINE SHOP WORK 



Fig. 305. Simple Tool Clamp 


Fig. 305 shows a 
simple form of tool 
clamp in which a variety 
of tools having square or 
rectangular shanks, such 
as inside boring tools, 
may be clamped, thus 
enabling the operator to 
use ordinary lathe tools for many 
simple jobs. 

Fig. 306 shows a turret- 
holder for a tool-post B, adapted 
to tools similar in form and pur¬ 
pose to those of Fig. 304, but 
with greater rigidity, as the 
shank A is secured in the tool- 
hole, and the cap screws CC hold 
it rigidly to the face of the turret. 

Fig. 306. Turret Holder for Tool-Post Fig. 307 shoWS a Well- 

designed box-tool device, providing for two tools and four back-rest 
jaws, all adjustable in any direction that may be necessary. At 




A is the shank to be entered in the tool hole in the turret; BB 
are the two tools; and CCCC are the four back-rest jaws. 


254 

























































































MACHINE SHOP WORK 


243 


The large tools that are bolted to the faces of the turret will be 
shown in the engravings illustrating turret-lathe operations. 

In Fig. 308 is shown a well-designed form of cross-slide, carrying 
two tools very rigidly secured and capable of adjustment in all 
directions horizontally; the tools may also be inclined. The base A 
supports the two tool-blocks carrying the tools BB. The base A 
may be moved transversely across the lathe-bed by means of the 
hand-wheel C , which is a very steady and well-controlled movement 
suitable for broad-faced forming tools or for facing tools; for narrow 



Fig. 308. Cross-Slide Carrying Two Tools 


or cutting-off tools, recourse is had to the rack-and-pinion device 
operated much more rapidly by the lever D. 

The tools held in the tool-holders (commonly called box tools), 
in tool-posts, or in the various styles of tool-holders for the cross¬ 
slide, and in many of the special tool-holders of fixtures, are usually 
short pieces cut from a square or rectangular bar of tool steel of 
suitable dimensions for the w r ork and the holding fixture. They are 
roughly shaped at the cutting point, hardened, and then ground to 
the form desired. In using what is commonly known as high-speed 
steel for these tools, short pieces are broken from the bar; and the 
proper forms for the cutting point or edge are obtained by grinding, 


255 



244 


MACHINE SHOP WORK 


no forging operation being necessary. While the forms usually 
used in lathe tools are also used in this class of cutting tools, there 
are many others, the particular form of work to be done determining 
their shape. 

Turret=Lathe Operations. The particular sphere of the turret 
lathe, and the use of the various tools and tool-holding devices, can 
be best explained by illustrating and describing some of the more 
important operations in the machining of castings of the usual 
forms. 

Some of the practical observations applicable to the handling 
of the work and the tools are given, and their importance should be 
fully realized by the novice in attempting turret-lathe work. 

Great care should be used to have all tools, tool-holders, attach¬ 
ments, fixtures, etc., securely clamped in place, so that there will 
be no danger of their working loose, and vibration will be eliminated 
as far as possible. 

The tools should be ground to the correct shape, and the finish¬ 
ing tools should be carefully stoned with a fine-grained oil-stone so 
that their cutting edges will be smooth and keen. They will then 
do much smoother work, and the cutting edges will last much longer. 

Generally there must be a roughing and a finishing cut, the same 
as in an ordinary lathe. In the turret lathe the two cuts are made 
by different tools, so as to avoid constant changes of adjustment. 

Stop-gages should be carefully set so that correct dimensions 
may be produced when the turret slide or cross-slide, as the case may 
be, is run firmly against the stop, but so that there is no straining or 
forcing of it. Unless care is used in this respect, correct dimensions 
cannot be maintained. 

Proper speeds must be used, according to the material to be 
machined and the diameter of the work. The same speeds will be 
used as for engine lathes. When tapping or threading dies are used, 
the speed, on the cut, must be very materially reduced. 

In chucking comparatively thin cylindrical work, it should be 
held by the outside, as there is much less danger of breaking it than 
if it is held by the inside. 

In machining heavy-rimmed balance wheels, they are frequently 
held by the inside of the rim so as to leave the outside and face clear 
for the tools. 


256 


MACHINE SHOP WORK 


245 


Pulleys and similar light wheels are frequently held by the 
arms, which rest against suitable supports so as to avoid distortion 
and to leave the rims and hub free for machining operations. 

In boring operations, particularly deep holes, the tool should be 
made with a long guiding end or pilot, which may enter a bushing in 
the main spindle of the machine before the tool commences to cut. 
This will reduce vibration and chatter, insure a true hole, and prolong 
the life of the tool. 

When the piece of work is comparatively long—that is, projects 
to a considerable distance from the chuck—the outer end should be 



Fig. 309. Turret Lathe Arranged to Machine Webbed Balance Wheel 


run in a center rest similar to that on an engine lathe, to hold it true 
and rigid, and to insure true and accurate work. 

Fig. 309 is a plan of the chucking arrangement; the turret and 
its tools; and the cross-slide tool-block of a turret lathe arranged to 
machine a webbed balance-wheel. It is to be finished all over, and 
must therefore require two operations. 

First Operation . The wheel is chucked as shown at A on the 
inside of the rim, by the chuck-jaws B. This leaves the outside of 


257 


































246 


MACHINE SHOP WORK 


the rim clear for the turning tools. The cored hole is first rough- 
bored with the cutter N in the end of a boring bar M, which is held 
in a steady rest or drill-support D. The hole having been rough- 
bored, the boring bar M is withdrawn, and the steady rest D thrown 
back out of the way. The turret is rotated so as to bring the bor¬ 
ing bar Mi into position. The forward end of this bar is supported 
by a bushing H in the main spindle. The two cutters N 1 and W 2 
are for roughing out the hole preparatory to using the taper reamer 
Q on another face of the turret. While boring with the bar Mi, the 
scale is broken on the web and hub by the tool-post tools shown at 



J and K. The scale on the periphery is broken by the tool J. The 
turret is revolved so as to bring the taper reamer Q into position, 
and the end of its bar enters a bushing in the main spindle. A taper 
bushing C is inserted in the taper hole for receiving the supporting 
arbor or pilot T in the facing head, as shown at the top of the engrav¬ 
ing. The balance-wheel is rough-faced, and the outer surface of the 
rim turned with the cutters E, G, H, and F in the facing head. This 
brings the piece approximately to size. For finishing these surfaces, 
the cutters Gi, Ei, Hi, and F 1 , in the finishing head are used, this 
head being supported in the taper bushing CV The finishing cuts 
are very light. 

Second Operation. These cuts being completed, the balance- 
wheel is removed from the chuck, reversed, and again placed in the 


258 



















MACHINE SHOP WORK 


247 


chuck, which has in the meantime been equipped with slip jaws of 
soft metal, bored out so as to exactly fit the curvature of the wheel. 
The piece is still further supported by a tapered arbor projecting 
from the hole in the main spindle and accurately fitting the taper- 
reamed hole. The turret is equipped with tools similar in form and 
purpose to those described. The scale is broken by tools in the 
rotating tool-posts, as in the first operation. The. first set of tools 
rough off the face of the rim and hub, and face the web. The second 
set finishes these surfaces completely, and the operation is completed. 

The operations for machining a spur-gear blank are well shown 
in Fig. 310. In this case a flat turret is used on the machine shown in 



Fig. 311. Turret Lathe Arranged to Machine Outside of Cone Pulley 


Fig. 299. At A is shown a section of the finished piece of work, 
giving the actual dimensions. The casting is chucked by the hub, 
as shown at B. At each of the other five faces the piece of work is 
represented in dotted lines, with the tool arranged in proper relation 
to it to make the required cut. The rough boring having been com¬ 
pleted, the turret is revolved to the next face, and the hook tool C 
faces the back of the hub. Upon the next turn of the turret, the 
boring tool D makes a finishing cut in the bore, bringing it to an 
exact diameter. Another turn of the turret, and the bar E, with its 
inside facing cutter, faces the rear side of the rim, while a facing cutter 
e faces the front of the hub. It will be noticed that the tool-holder II 
travels along the slide J , thus providing for the necessary feed for 
both the tools E and e. The next movement of the turret brings into 


259 




248 


MACHINE SHOP WORK 



action the finishing tools F and/, which finish the rear face of the rim 
and the front face of the hub, operating in a similar manner to the 
tools E and e. A final turn of the turret brings the round-nosed turn¬ 
ing tool G into position, and turns the outside diameter of the gear 
blank, completing the operation. Upon this machine, provided with 
the tools shown and operated as described, an iron casting of the 
dimensions given can be completely machined by an expert operator 
in from eight to ten minutes. The same work done upon an engine 
lathe would require four or five times as long. 

A much more complicated series of operations is presented in 
Figs. 311 and 312. In Fig. 312 is shown the first of the series of 


Fig. 312. Arrangement for Machining Inside of Cone Pulley 

operations, comprising the machining of the inside of the cone. In 
Fig. 311 the series of operations necessary to finish the outside are 
shown. Referring to Fig. 312, it will be seen that the cone-pulley 
casting A is supported upon the second step from the small end by 
the cylindrical base B. Within this the three jaws of the chuck grasp 
the smallest step of the cone, holding it very rigidly and securely in 
place. The boring bar C carries the cutters for rough-boring the 
cored hole. Its inner end is supported by a bushing in the main 
spindle, as shown in Fig. 309. The next turn of the turret brings the 
boring bar D into action, which finishes the hole to the proper diam- 


260 




MACHINE SHOP WORK 


249 


eter. The next tool E faces the edge of the rim on the largest step of 
the cone. The face F of the turret carries no tool. Tool G is a very- 
important, compound tool whose work is to finish the inside of the 
larger three steps, and also to face the annular surfaces between the 
steps. It consists of a massive casting, bolted to the turret face and 
divided into three double-ended arms, each of these ends carrying a 
tool of proper form for the inside turning and facing, making six 
tools in all. Through the center of this tool-holder is an arbor or 
steadying bar g , which passes through the bushing in the main 
spindle and holds the tool-carrier steady and in its proper central 
position. The tool II serves to finish the inside of the largest step, 
for a short distance from the face, to the accurate diameter for 
fitting the flange that supports this end and furnishes a hub through 
which its shaft or spindle passes. 

The second series of operations is shown in Fig. 311. These 
operations consist of machining the outside of the cone-pulley casting 
A, that portion of the inside of the larger end finished by the tool II 
in the first series of operations fitting over a circular disc B , through 
slots in which the chuck jaws are forced outwardly against the cone 
casting. In fixing the casting in position, an arbor C projects from 
the bored hole, and is entered in a reamed hole of the same diameter 
in the centering fixture D attached to the turret, whereby the outer 
end of the cone-pulley casting is quickly and accurately centered. 
This fixture also serves as an excellent support; for the outer end of 
the cone during the process of turning and facing the outer surfaces. 
The special revolving tool-block E carries on one side five tools for 
turning the outside of the cone steps, as shown in the illustrations, 
and, on the opposite side, five facing tools for facing the annular 
surfaces between the steps. In the operation of turning the outer 
surfaces, it is necessary to crown them that is, to make the center of 
each step of slightly larger diameter than at the two edges, as in 
ordinary pulleys. To accomplish this, the taper attachment F is 
brought into use, being set to give the larger diameter on the side 
toward the chuck and turning half the width of the outer surface; the 
setting is then reversed for turning the other half. As all five sur¬ 
faces are turned or faced simultaneously, the operation is very rapid 
when compared with the work of an engine lathe. The inside of the 
small end of the cone is finished with the tools G and II in the usual 


250 


MACHINE SHOP WORK 


manner. In all turret operations, the lateral travel of the turret is 
controlled and limited by the revolving multiple-stop device at J . 

There are many devices and adjunct fixtures in use upon the 
turret lathe; and their number, as well as the ingenuity of their design 
and the extent of their usefulness, is constantly increasing. So 
numerous are they that no attempt is here made to show and describe 
them. The same, in a lesser degree, may be said of the turret-lathe 
tools. At the same time, there is a very large range of work con¬ 
stantly done on turret lathes with the most ordinary equipment. It 
was formerly assumed that the turret lathe could be used with econ¬ 
omy only when at least a hundred pieces were to be machined. It is 
ordinary practice at the present day to use the turret lathe when as 
few as a dozen pieces (and sometimes less) are required. As the 
value of the turret lathe and its efficiency come to be better under¬ 
stood, its usefulness is better realized and appreciated. 

AUTOMATIC SCREW MACHINES 

The automatic screw machine, in its design and method of 
operation, is a highly developed type of turret lathe, its cutting tools 
being carried in some form of turret. By the term turret, as used in 
this connection, is understood a revolving, multiple tool-holder, 
whether rotating on a vertical or on a horizontal axis; and whether 
consisting of a single casting having the necessary tool-carrying 
appendages, or of a cylindrical form carrying a series of sliding, tool¬ 
carrying spindles. The principles upon which it is designed and 
constructed, and upon which it operates, are the same. 

The automatic screw machine, as originally designed, was 
intended principally for making small screws and studs; hence it 
was called a screw machine. The flexibility of its plan, and its 
adaptability to a large range of operations, encouraged its develop¬ 
ment along other lines of work. Normally it was adapted to making 
screws, studs, and similar work from a bar, which was passed through 
its hollow spindle from the back of the machine, and was pressed 
forward against a stop carried in one of the tool-holes in the turret 
whenever the chuck was opened sufficiently to release the bar of stock. 
The device which fed the bar through was operated by a weight, and 
was called a wire feed, originally from the fact that screws were made 
from pieces of straightened wire. The same device, built of sufficient 


262 


MACHINE SHOP WORK 


251 


weight and strength, is capable of feeding quite large bars of stock 
through a machine of many times the capacity thought possible 
in the early years of the development of this machine. This 
wire feed device operated automatically, it only being required to 
introduce a new bar when that in the machine was used up. 

The predominant feature in the design of the automatic screw 
machine, after the use of the turret, is the employment of drum cams, 
upon which are fixed a series of removable cam members suitable 
to the piece of work to be made, and by wdiich the automatic move¬ 
ments of the different operative parts of the machine are produced. 
It is because of the action of these cams that the machine is classed 
as automatic. 

By automatic, we mean a machine in which all of the movements 
are mechanically made, including the bringing of a new length of 
work through the chuck, upon which the various operations are made 
in succession so that the operator has only to keep the cutting tools 
sharp and to put in another bar of stock when one has been entirely 
used up. By semi-automatic, we mean a machine in which the rough 
piece of work is placed in the chuck by the operator, and on which all 
the various operations—such as drilling, boring, reaming, forming, 
facing, etc.—are mechanically performed, as well as the rotation of 
the turret. Thus the machine operating on bar work can readily be 
made automatic in a strict definition of the term; while if the pieces 
are small and separate castings, drop forgings, and the like, they must 
be placed in the chuck by the operator, and the chuck closed, before 
the automatic work of the machine commences. 

There are built, however, machines of this class, in which the 
castings or drop forgings are placed in a sort of magazine or hopper, 
whence they pass to the chuck, in which they are gripped ready for 
the subsequent machining operations, this work being entirely auto¬ 
matic and the only attention required from the operator being that 
of keeping the magazine full of pieces and the tools sharp and properly 
adjusted. 

Types of Automatic Screw Machines. Manufacturing Auto¬ 
matic Chucking and Turning Machine. Fig. 313 shows a Potter and 
Johnson machine, called by them a manufacturing automatic 
chucking and turning machine. It is a good example of a semi¬ 
automatic machine which has nearly all the features of the typical 


263 


252 


MACHINE SHOP WORK 


automatic screw machine, and at least one feature that is not adapt¬ 
able to a machine making the pieces of work from a bar run through 
the hollow spindle and carrying cutters by which the back of a piece 
of work held in the chuck is automatically faced. This is accom¬ 
plished through the lever C, rod D, and cam E. 

The headstock is triple-geared so as to provide for ample power 
for heavy work, this gearing being changed to the desired speeds by 
a simple lever mechanism. The turret is mounted in the same man¬ 
ner as in a turret lathe, upon a laterally moving slide. This, however, 
is actuated by suitable connections to the drum cam A, the cam 



Fig. 313. Automatic Chucking and Turning Machine 
Courtesy of Potter and Johnston Machine Company, Pawtucket, Rhode Island 


tracks of which are composed of removable plates BB fitting the 
surface and attached by screws. The turret has five faces; conse¬ 
quently there are five sets of these plates, which may be so shaped 
and arranged as to give any length of stroke desired. Usually a full 
stroke is given to the turret slide, the act of cutting being confined 
to the latter part of the stroke. The cross-slide is equipped with 
two tool-posts FF; and the tools can be arranged to work at the same 
time that the turret tools are cutting—or separately, as the nature 
of the work may require. The cross-slide may also be provided with 
tool-blocks for carrying blades or forming tools for special work. It 
is operated through a rack-and-pinion device from a cam G, and the 
triangular actuating blocks upon this cam can be adjusted in any 
required positions around the circle that may be necessary to produce 


264 




MACHINE SHOP WORK 


253 


the required movements. The cams A, G, and E are fixed to the 
same shaft, which makes but one revolution during the cycle of 
movements necessary to complete one piece of work. This feature 
is the same in all the different types of this class of machines. 

While the machine shown was designed for handling separate 
pieces of work, as castings, drop forgings, etc., the removal of the 
back facing bar, and the substitution of a wire or rod feed with an 
automatically operated chuck, would convert it into a machine 
adapted to machine pieces automatically from the bar. 

The latest type of Potter and Johnston chucking and turning 
machine is shown in Fig. 314. 

Cleveland Automatic Machine. Fig. 315 shows a Cleveland 
automatic machine, of which several variations of the same style 



Fig. 314. Latest Type of Automatic Chucking and Turning Machine 
Courtesy of Potter and Johnston Machine Company, Pawtucket, Rhode Island 

are built. The main spindle A is driven from the system of pulleys 
B, the belt being controlled by the automatically operated shifter C. 
At D is shown the device for opening and closing by hand the chuck 
in the head E of the main spindle A when setting the machine. 
The mechanism by which the bar of stock is forced forward through 
the chuck, is at F. 

The turret mechanism is at G, and consists of a cylindrical device 
with its axis in a horizontal position and journaled in the housings at 
H H, sliding in the left-hand housing in making the cut. This form 
of turret is exceedingly rigid. The tool-holes are bored in the end of 


2G5 







Fig. 315. Cleveland Automatic Machine Shown for Analysis 









MACHINE SHOP WORK 255 

the cylindrical portion g } and the tools secured by set screws, as 
shown. T. he turret is moved forward and back by a mechanism oper¬ 


ated by the shaft N; and is revolved on the back stroke by suitable 
helical cams, a portion of which is shown at K • In setting the 


267 
















256 MACHINE SHOP WORK 

machine, the turret is operated by the crank M, upon whose shaft is 
a worm engaging the worm wheel J . 

The cross-slide L is arranged for two tool-posts, and is operated 
by a suitable mechanism in the rear. It is adapted for carrying form¬ 
ing tools as well as the usual cutting-off tools. 

There are a number of interesting and valuable attachments 
furnished with these machines, among which is one for slotting screw- 
heads, and for slabbing or milling at a time, two sides of square or 
hexagonal heads by a straddle mill. There is also a third spindle 


Fig. 317. Universal Multiple-Spindle Automatic Screw Machine 

speed attachment, in which the center pulley B, usually an idler, is 
•utilized as a driver; and by the addition of a set of differential gears, 
the spindle speed is reduced in a ratio of three to one, giving a slow 
speed for threading large work. By this means the spindle speed 
can be as rapid as is possible for the use of high-speed steel tools, and 
still have a slow speed available for large tapping or threading. 

In case solid dies are used and the threading done with the belt 
on the pulley B (now a driver), the belt is thrown to one of the other 
pulleys, and the fast reverse speed used to run the die off the work. 
A magazine attachment is also made for automatically feeding cast¬ 
ings or drop forgings down to the chuck, so as to dispense with the 


268 




MACHINE SHOP WORK 257 

services of the operator on this class of work, except to see that the 
magazine is kept supplied with work. 

In Fig. 316 is shown the latest type of Cleveland “automatic” 

Universal Multiple-Spindle Automatic Screw Machine . This 
machine, Fig. 317, is of a type distinctively different from either of 
the previous examples. The operative parts are operated mostly 
by the usual drum cams, three of which, A, B, and C , are used. 
The peculiarity of the design of this machine is that the work is 
carried in five revolving spindles at D , while axially opposite them 
are five tools. The revolving spindles carry five bars of stock, upon 
all of which work is being done simultaneously. The results secured 
by this arrangement are that the work necessary for completely 
finishing a piece is no longer than that required for performing the 
longest single operation, regardless of the number of operations 
required on the piece. 

The machine is driven by a single belt upon the pulley F, the 
power being transmitted by spur gearing to the center shaft G, which 
runs through the spindle head H, at the left of which it is connected 
by spur gears with the five spindles at D . There are three cross¬ 
slides J , K f and L, the tools of which act at the same time as the box 
tools or other tools usually carried in a turret. The cam shaft carry¬ 
ing the cams A, B f and C is driven by a belt from the pulley M to 
the two pulleys N, which, by means of differential gearing, give two 
speeds to the shaft; on the latter is a worm engaging the worm wheel 
P, thus providing for a rapid speed for indexing, and a quick advance 
and return of the toois. The belt is shifted automatically to the 
inner pulley, which drives the shaft slower for the feeding of the 
tools on the cut. The squared end of the cross-shaft provides for 
a crank which may be used to rotate the mechanism when setting the 
machine. 

The design of the machine is very ingenious, and its output on 
small work should be very large in consequence of having five or more 
tools continuously employed during the time that in the usual type 
of machine there is one (or, at most, two) in active operation. 

Brown and Sharpe Automatic Screw Machine. This machine, 
shown in Fig. 318, is of a type quite distinct from any of those above 
described. It will be noticed that the machine is very compact when 
compared with some of the others previously illustrated. This 


269 


258 


MACHINE SHOP WORK 



being the case, it is necessary to show sectional and other views, 
in order properly to explain the mechanism so that it may be 

understood. 

Fig. 319 is a front 
elevation showing a sec¬ 
tion through the spindle, 
spindle boxes, pulleys, 
etc. The main spindle 
runs in phosphor-bronze 
boxes. The front bearing 
is adjustable, and is ad¬ 
justed by nuts 1 and 2 . 
The thrust is taken by a 
hardened steel washer 5 , 
and adjusted by the nut 
4 . Friction clutch pulleys 
10 , running on ball bear¬ 
ings, drive the spindle. 

Fig. 320 is a rear ele¬ 
vation of the machine, 
and is introduced to illus¬ 
trate more completely 

Fig. 318. Brown and Sharpe Automatic Screw Machine. construct i on . 

Courtesy of Brown and Sharpe Manufacturing Company, The friction dutches 

Providence, Rhode Island A 

are conical; the clutch bodies 11 , Fig. 319, are forced into the pulleys 
by sliding the sleeve over the levers 12 , which have for one fulcrum 



the screw in the clutch body, and for the other a notch in the 
spindle. To adjust for wear, loosen clamp screw 15 , and turn nut 13 . 


?70 
































































MACHINE SHOP WORK 


259 


The clutch sleeves are set central, to give an equal pressure on 
both pulleys, by means of the screws 27. In making this adjustment, 
there is a slight play allowed in the clutch fork to avoid friction, 
except at the point of reversal. 

The spindle is reversed to run backward by the spring plunger 
42 , which, when released, instantly engages the clutch with the 
pulley nearest the chuck. To run forward, the clutch is reversed by 
the cam 21, to engage the other pulley. This cam is operated by 
the clutch 32, and at the end of the revolution is drawn out by the 
lever 23. At the time of reversing the spindle to run forward, the 


ff 



Fig. 320. Rear Elevation of Brown and Sharpe Automatic Screw Machine 


action of the cam compresses the plunger spring ready for the next 
reversal; the plunger is held in place by the wide part of the lever 22. 
The levers 22 and 23 are lifted to reverse the spindle at the proper 
time, by adjustable dogs on the carrier, shown below them in Fig. 319. 
If the work is to be threaded, this carrier shaft is connected by the 
positive clutch 24 to the cut-off cam shaft 18. When changing 
cut-off cams, the clutch is disengaged and can remain in this posi¬ 
tion, for work not threaded. Should it be desired to both thread 
and tap work, or to cut two threads on the same piece, two or more 
sets of dogs can be used on the carrier. 

The spring collet that holds the stock has no end movement, 
thus providing for the accurate feeding of the stock regardless of 
slight variations in size. It is closed by means of the sleeve 6, 


271 






















































260 


MACHINE SHOP WORK 


Fig. 319, which is tapered inside and slides over the collet. This 
sleeve is operated by the tube extending through the spindle to the 
chuck-levers 7, which in turn are operated by the sleeve 8 through 
the lever and cam 25. The chuck mechanism is operated and the 
chuck fed by the cam 25, which is driven through spur gears S3, by 
the positive clutch 39 on the driving shaft. By depressing the lever 
underneath the clutch, shown in Fig. 320, the clutch is engaged and 
makes one revolution; it is then disengaged by the pin in the lever 
acting upon the cam surface of the clutch, and returns to its original 
position. 

To adjust the chuck, the nut 17 is loosened, and the nut 16 
turned until the holding capacity of the chuck is properly regulated; 
then the nut 17 is tightened, and both nuts are locked by means of 
the spanner wrenches provided. 

The main feed-shaft U is driven by the pulley shown at the head 
of the machine. This pulley is engaged by a positive clutch oper¬ 
ated by the starting lever 21, Fig. 319. Thus the feed is always 
under complete control. A hand wheel provided with a handle is 
used for operating the mechanism when setting the machine. 

The stock is fed in the usual manner by a feed-tube, the outer 
end of which is connected by a latch to the slide 28. This slide has 
a slot in which is a sliding block connecting it to the lever 29, which 
in turn is operated by the cam 25. The sliding block is adjusted by 
a screw and crank, as shown in Fig. 320, and, as the lever 29 always 
moves a fixed distance, the length of feed is regulated by varying the 
position of the block. A graduated scale is mounted on the slide, 
and indicates the length of feed. 

The feeding fingers are changed by lifting the latch at the rear 
end of the tube, and withdrawing the feed-tube. These fingers are 
threaded left-hand. 

When it is desired to feed more stock than the usual capacity of 
the machine, two or more dogs can be used on the left side of carrier 
19, Fig. 319, and the feeding mechanism operated several times. 

The turret 1^5 is mounted vertically on the side of the turret 
slide, Fig. 319. It has a long taper shank that forms the bearing in 
the turret slide, and is rotated by a hardened roll in the disc 35, 
Fig. 320, which engages the radial grooves in the disc 31f. on the rear 
end of the turret shank. The revolutions of the turret are thus 


272 


MACHINE SHOP WORK 


261 


made very rapidly and with no noticeable shock. It is locked in 
position by a hardened taper pin which is withdrawn by a cam. 

The turret slide receives its forward motion for the cutting tools 
through a bell-crank lever operated by a cam on the shaft 40, Fig. 320, 
which is driven through spur gears by the shaft and worm gear 41 • 
The quick return and advance of the turret slide, and the revolv¬ 
ing of the turret, are controlled independently of the turret-slide 
feed-cam, by a crank, while the roll on the bell-crank lever is passing 
from the highest point of the turret-slide feed-cam to the point of 
starting the next cut. The crank is operated by gears at the rear of 
the machine, driven by the positive clutch 88, Fig. 320, on the driv¬ 
ing shaft, with lever and other parts for making one revolution, as 
described in connection with the feeding mechanism. As the crank 
revolves, it allows a spring to return the turret slide without the 
rack. The turret is then revolved as described; and when the crank 
comes to rest after making one complete revolution, the machine is 
ready for the next operation. 

The cross-slides are operated by the cut-off cam shaft 18, 
Fig. 319, which is driven through bevel gears by the worm-wheel 
shaft 41 , Fig. 320. 

The front slide has a direct lever or segment of a gear; the back 
slide has, in addition, an intermediate lever or segment to reverse the 
motion, thus bringing the cams for operating both slides into a 
convenient position. The form of that part of the cam controlling 
the quick movement of the slides is the same for both. The seg¬ 
ments mesh into racks that extend beyond the slides. The outer 
end of these racks is threaded and provided with nuts for adjusting 
the cuts of the tools. Stop-screws are also provided to insure 
accuracy in forming. 

The cross-slide tools have circular shanks, and are held in place 
by screws. Eccentric nuts are provided on screws that allow the 
tools to be easily and quickly adjusted to the proper height. These 
tools are sharpened on the face without changing the outline, the 
same as formed milling cutters. 

The tools are lubricated by a geared oil-pump of ample capacity, 
provided with suitable piping. The pump is not stopped with the 
disengaging of the feed-clutch, thus insuring a large, steady stream 
of oil as soon as the tools begin to cut. 


273 



262 MACHINE SHOP WORK 

In Fig. 321 is shown a No. 2 Brown and Sharpe automatic 
screw machine. 

Hollow Mills. For turning the bodies of small screws, the 
shoulders on studs, and many similar operations, hollow mills are 
used. A simple form of one of these is shown in Fig. 322, which has 
three cutting edges. An improved form is shown in Fig. 323, con¬ 
sisting of a collar through which pass three set screws, their points 


Fig. 321. Number 2 Automatic Screw Machine 
Courtesy of Brown and Sharpe Manufacturing Company, Providence, Rhode Island 

bearing upon each of the cutting sections, by which means they can 
be adjusted when so worn that work comes too large. A better form 
of the hollow mill is shown in Fig. 324, which is constructed with three 
adjustable blades, whereby the tool may be set for a considerable 
variation in diameter. 

Setting=Up the Machine. A variety of types of automatic screw 
machines have been shown and described, in order that the reader 


274 








MACHINE SHOP WORK 


263 



Fig. 322. Hollow Mill with Three 
Cutting Edges 


may familiarize himself with those built by different manufacturers, 
and so be able to handle whatever kind he may be required to set-up 
for the job in hand. The great variety of work which the turret 
lathe and the screw machine are 
called upon to perform, renders it 
impossible to describe all the oper¬ 
ations necessary for such work; 
but a few general directions may 
be given that will nearly always 
apply: 

When making work from the bar, it is first necessary to select 
and place in the machine the proper chuck, and to arrange at the rear 
end of the main spindle for the support of that end of the bar. If a 
rod feed is used, that is next attended 
to. A stop is now fixed in one of the 
tool-holes in the turret, against which 
the end of the bar is forced by the 
automatic rod-feed. This stop is set 
so that the bar may be forced out of 
the chuck only far enough to make 
the required piece, and to furnish 
space for the cutting-off tool of the 
tool-slide to work. The box tools should next be set, and the cut¬ 
ters adjusted to the diameter. The adjustable stops for the travel 
of the turret for each cut will now be adjusted, the machine started, 
and each tool brought into action 
and its adjustment corrected. Sup¬ 
posing that two box tools are used, 
the stop will be in tool-hole No. 1, 
and the box tools in Nos. 2 and 3. 

If the job requires very accurate di¬ 
ameters, a roughing and a finishing 
box tool will be needed for that por¬ 
tion requiring the delicate work. 

This will be No. 4. If the smaller 
diameter is to be threaded, the die will be set in No. 5. If this 
is a solid die, the belt shifter must be set, by the proper location 
of the dogs on the shifter cam to produce the reversed motion for 



Fig. 323. Improved Hollow Mill 



Fig. 324. Hollow Mill with Three 
Adjustable Blades 


275 
























264 


MACHINE SHOP WORK 


backing off the die, and then for the forward motion of the next cut. 
A pointing tool may be set in No. 6 for finishing the end of the piece 
after the thread has been cut. The cutting-off tool is now adjusted. 
In some cases the back tool of the cross-slide is made a forming tool 
for finishing the end of the piece that is to be cut from the bar, or 
for rounding or chamfering it; after which the cutting-off tool 
advances and severs it from the bar. These operations having been 
provided for, the chuck-operating cam is adjusted to open the chuck 
at this point, permitting the rod-feed device to force the bar through 
and against the stop in tool-hole No. 1, after which it should immedi¬ 
ately close on the bar, and the cycle of movements be repeated. 
The drum cam for producing the lateral movement of the turret will 
not usually need to be changed. The mechanism for revolving the 
turret will ordinarily be left without readjustment in setting-up the 
machine for a new job. 

If separate pieces, as castings or drop forgings, are to be 
machined, the first operation is usually boring the hole; then reaming 
it. If a considerable degree of accuracy is required in the diameter 
of the hole, there will be a roughing and a sizing cut before using the 
reamer. The succeeding cuts will depend so much upon the shape 
and the necessary working surfaces of the piece, that no general 
sequence of operations can be given. 

There is probably no machine in the modern manufacturing 
plant that requires greater ingenuity and fertility of resources than 
the selection and setting-up of the automatic machine so as to realize 
the greatest measure of economy and efficiency. 


276 




















FIXED CROSS-RAIL MILLING MACHINE MILLING AUTOMOBILE CASTINGS 

Courtesy of Ingersoll Milling Machine Company , Rockford , Illinois 



















MACHINE SHOP WORK 


PART V 


MODERN MANUFACTURING 

Machine Building vs. Machine Manufacturing. While machine 
work in general, and the use of machine tools in particular are 
much the same in all shops, the methods employed in machine 
building and in machine manufacturing are essentially different. 

Construction Methods. In machine building only a small num¬ 
ber of machines are built in a single lot and it is seldom that they 
are worked upon in any consecutive order. For example, while 
several machines of the same kind may be under construction, they 
may stand in all stages of construction from that of those nearing 
completion or even completed to some upon which construction has 
just begun. In some shops, this is so much the fact that machines 
are constructed only after the order for them has been placed. When 
manufacturing machines, however, the process is a very different 
one. Here the work is done in lots of considerable size and each 
operation on each piece is consecutively performed. 

Types of Workmen. The workmen in a shop producing 
machines by manufacturing methods are differently placed than they 
are in shops building machines in small lots, perhaps a machine at 
a time only. In the latter case the workmen may, during the same 
day, perform lathe work, milling, drilling, bench, and floor work; 
while in a shop which manufactures machines in considerable lots, 
the workmen usually works on one machine during the term of 
employment. This has led to the development of workmen who 
term themselves lathe hands, planer hands, etc., each workman 
specializing in the handling of a single machine tool and seeking 
employment as a specialized machinist. In certain shops, notably 
those building automobiles, this specializing process has proceeded 
to such an extent that the workman performs but a single operation 
on a machine. For example, he may be employed on a lathe to square 
up the end of crank shafts, which come to him in sufficient quantities 


279 



266 


MACHINE SHOP WORK 


to keep him continuously employed during his working day. If 
the shop is run on a twenty-four hour, three-shift basis, he may in 
this case be one only, of three workmen, each of whom does the same 
operation on the same single purpose machine. 

PRODUCTION METHODS 

Single Purpose Machines. If the reader has carefully followed 
the above, he will realize somewhat the extent to which modern 
organization of workmen has proceeded. Another development 
has been the construction of single purpose machines. For example, 
Fig. 350, page 294, shows a machine constructed for the single 
purpose of drilling the clearance holes on solid threading dies. On 
this machine a single operation only can be performed, but by the 
use of four spindles and five work-holding chucks, a die is com¬ 
pletely finished at one stroke of the table. Single purpose machine 
tools of any sort can now be bought in the open market, as, for exam¬ 
ple, single purpose lathes, grinding machines, etc. 

In other cases, instead of purchasing single purpose machines, 
the regular types have been changed by the use made of special 
attachments, tools, jigs, and fixtures, to perform either a single 
operation only, or at least a slight range of operation. 

Specialized Cutting Steels. Modern investigations have led 
to the adoption of specialized cutting methods and cutting tools 
in up-to-date manufacturing. At the very center of these shop 
efficiency methods stands the newer types of cutting steels. These 
have so revolutionized metal cutting Operations that production 
has been in many cases more than doubled. 

Cutting Lubrication. By means of properly designed machines 
and pumps, and by experiment in the uses and nature of numerous 
oils and mixtures, it is now common practice in some lines of cutting 
to practically submerge the cutting operation with some one of the 
several cutting lubricants. 

Cutting Speeds. These have been increased from the older 
series of possible cutting speeds to an extent which has led one 
enthusiast to predict that the time was not far distant when steel 
and iron would be cut as rapidly as wood. 

Cutting Feeds. The great increase in the weights and con¬ 
sequent rigidity and massiveness of the present-day machine tools, 


280 


MACHINE SHOP WORK 


267 


as well as the modern work-holding devices, has made possible an 
increased feeding of the cutting tool little thought of by the older 
machinist. 

Automatics. Under this head may be classed those machines 
which produce the work in a more or less completely finished state 
with the least attention. While no machine is so constructed that 
it can be classed as fully automatic, there are many on the market 
which are so complete in their action that a single attendant will 
care for and keep in operation as many as a dozen machines. 

Automatic Control. Much advance has been made in recent 
years in devising means of controlling the operation of machines 
from a central point. Electrical, hydraulic, and pneumatic devices 
have been and are being introduced which have for their objective 
the possibility, when once the machine has been adjusted, of con¬ 
trolling its operations by the movement of a lever or the pressing 
of a button. Such a control is already in certain use upon large 
planers, boring mills, etc. 

Cold Worked Metals. It has been found that certain machine 
parts, such as screws, shafts, pulleys, etc., can be formed into their 
proper contours by pressing, rolling, or squeezing processes, in a 
manner which admits of a lesser first cost, than that of cutting them 
from the solid in a lathe, milling machine, or other machine tool. 
As this work is performed without a previous heating of the stock, 
it is classed as “cold working’’. 

Die Casting Machine Parts. This process consists in casting, 
in suitable closed dies under pressure, a previously melted alloy. 
Parts of small and delicate machinery as well as instruments 
are often produced in this manner so accurate in dimension and 
perfect in finish that they are assembled without added machine 
work. 

Special Molding Processes. Machine manufacturing is in many 
cases confined to producing a machine, many of whose parts are 
made of iron castings in which exact accuracy of fitting is not neces¬ 
sary. The ordinary loom and certain lines of agricultural machinery 
are notable examples of such machines. By construction of special 
molding processes, notably that of machine molding, it is possible 
to produce many machine parts sufficiently accurate to render them 
directly usable after having been cleaned and common snags removed. 


281 


268 


MACHINE SHOP WORK 


Special Die Forgings. While the ordinary forged piece is 
seldom suited for use in accurate machine construction without 
previous machining, several firms are now producing special die 
forged machine parts of an accuracy in dimensions and perfection 
of finish that leaves little to be desired. 

Heat Treatment. Under this head comes the modern method 
of giving to many machine parts such as spindles, shafts, gears, 
cones, clutches, and many others, a special heating and cooling 
treatment. The production' performances of our modern machines 
are in many cases made possible only because the constructor has 
learned that certain steel parts when heated and cooled in a pre¬ 
determined scientific manner are given an added. strength to 
resist wear or breakage. 

Ball Bearings. The use in machines of specialized ball bear¬ 
ings has gained rapidly in recent years. While in the case of machine 
tools their use has been more largely confined to such machines 
as drillers, their certain use is everywhere self-evident. 

Bearing Alloys. Where accuracy of bearing and closeness of 
fitting is especially desirable, the older type of plain bearing is 
believed by many machine construction engineers to be the better. 
To ensure the proper wearing qualities under the varying conditions 
of service, it has become desirable that the several bearing alloys 
be carefully studied and their characteristics tabulated. 

Bearing Lubrication. Correct proportions of bearing surface 
to the load, a suitable bearing alloy, and assured bearing lubrication 
are sought. In studying bearing lubrication, all these must be 
considered. 

Drives. Belt Drives . The belt manufacturer has helped to 
solve this problem by producing belting suited to the machine con¬ 
structor’s needs. Most conditions of temperature, humidity, and 
pliability have been met by the belt-maker. Many experiments 
have been made and published by engineers to show what a given 
belt may be expected to do under varying conditions of heat, cold, 
and dampness. 

Geared Drives. Machines designed for heavy roughing cuts 
are often provided with a complete geared driving mechanism in 
which all the speed changes are made through trains of gearing and 
engaging clutches. 


282 


MACHINE SHOP WORK 


269 


Motor Drives. Instead of driving by means of trains of belting 
there is an increasing tendency toward the use of direct driving. 
This is usually done by direct connection of an electric motor to 
the driving mechanisms. In shops where the machines are fitted 
with individual motors, it may be so complete that no belting is 
to be observed. 

Jigs and Fixtures. Where strict interchangeability of parts is 
essential, special work-holding and tool-locating devices are indis¬ 
pensable if a low manufacturing cost is to be attained. These are 
known as jigs and fixtures. 

Time Study. The nearer to a minimum cost a machine can 
be constructed while maintaining a proper commercial standard, 
the greater are the chances that the business will be successful. 
It is, therefore, among other things, extremely important that the 
lowest possible labor cost shall be ascertained. In modern efficiency 
work, an exhaustive time study is made of each operation performed 
in the shop until definite time figures are obtained and recorded in 
the manager’s office. 

Motion Study. This term is used to designate that particular 
line of investigation which has for its objective the elimination 
of all unnecessary movements in performing a given piece of work. 
Investigation has shown that an untrained workman when per¬ 
forming even the simplest of operations may, and usually does, make 
many entirely useless movements to get his results. 

Overheads. Under this name are classed all those expenses 
of manufacture which cannot be as directly charged to production 
as can labor cost and the cost of materials. They include such 
items as heat, power, light, insurance, depreciation, taxes, office 
help, executives, beside others, and are known as the shop burden. 

Selling Costs. The cost of selling the manufactured machines 
may or may not be charged to their cost under the head of “over¬ 
heads”. In any ease it must be at least approximated if not exactly 
known and, of course, charged along with the previous items to the 
production costs. 

PRODUCTION MACHINES 

The brief review of modern machine methods given in the 
preceding pages indicate the trend of the developments being made 
by the progressive construction engineers. The modern machine 


283 


270 


MACHINE SHOP WORK 


constructor makes use of the work of scientists whenever it touches 
his line of production, and in fact is ever reaching out and searching 
the world for new production ideas. In the following section will 
be briefly described and illustrated a few of the more modern special 
or specialized machine tools used in machine manufacturing. 


GRINDING MACHINES 

Range of Usefulness. While in many shops the grinding 
machine is used only as a finishing tool on parts which require a 



Fig. 325. Example of Steady Rests as Employed by Norton Grinding Company 
Courtesy of Norton Grinding Company, Worcester, Massachusetts 


special surface, or in which greater accuracy is required than is 
readily reached by the other machine tools, in modern work shops 


284 





MACHINE SHOP WORK 


271 


it is one of the large production factors. The work which comes 
to the grinding machine has usually been rough turned to an approx¬ 
imate diameter, but in many instances it has been found that the 
grinding machine will completely finish the piece of work from the 
rough stock at a lesser labor cost, doing its own roughing and finish¬ 
ing. This is especially true when long slender shafts are produced. 
Automobile crank shafts, for example, are commonly ground from 
the rough. 

Cylindrical Grinding. Producing cylinders of revolution is 
one of the more common uses to which grinding machines are put. 
This is usually accomplished by traversing a rotating abrasive wheel 



Fig. 326. Traverse Markings on Piece of Ground Work 


in contact with the rotating piece of work, as in Fig. 325. In this 
operation the rotating wheel can be made to feed along the length 
of the work by giving the work table a traversing motion along 
the bed of the machine. Some of the things to be noted in this 
machine are: (a) Its large wheel spindle with generous journals 
making it possible to use abrasive wheels large in diameter with 
broad faces; (b) the abrasive wheel bearing stand giving large 
spindle bearings and great rigidity; (c) a heavy traversing table 
with large bearing area upon the bed; (d) the work-supporting 
rests; and (e) the general massiveness of construction. 

Wheel Speed. The peripheral or surface speed of the abrasive 
wheel is usually held pretty closely to 5500 linear feet per minute. 
While in some cases a wheel speed of 6500 feet per minute or as 


285 






272 


MACHINE SHOP WORK 


TABLE XI 

Revolutions per Minute for Various Sizes of Grinding Wheels to 
Give Peripheral Speed in Feet per Minute 


Diameter 
of Wheel 
in Incke.-, 

4003 

4503 

5000 

5500 

G000 

6500 

1 

15,279 

17,200 

19,099 

21,000 

22,918 

24,850 

2 

7,639 

8,590 

9,549 

10,500 

11,459 

12,420 

3 

5,093 

5,725 

6,366 

7,000 

7,639 

8,270 

4 

3,820 

4,295 

4,775 

5,250 

5,730 

6,205 

5 

3,056 

3,440 

3,820 

4,200 

4,584 

4,970 

G 

2,546 

2,865 

3,183 

3,500 

3,820 

4,140 

7 

2,183 

2,455 

2,728 

'3,000 

3,274 

3,550 

8 

1,910 

2,150 

2,387 

2,635 

2,865 

3,100 

10 

1,528 

1,720 

1,910 

2,100 

2,292 

2,485 

12 

1,273 

1,543 

1,592 

1,750 

1,910 

2,070 

14 

1,091 

1,228 

1,364 

1,500 

1,637 

1,773 

16 

955 

1,075 

1,194 

1,314 

1,432 

1,552 

18 

849 

957 

1,061 

1,167 

1,273 

1,380 

20 

764 

860 

955 

1,050 

1,146 

1,241 

22 

694 

782 

868 

952 

1,042 

1,128 

24 

637 

716 

796 

876 

955 

1,035 

26 

586 

661 

733 

809 

879 

955 

28 

546 

614 

683 

749 

819 

887 

30 

509 

573 

637 

700 

764 

827 

32 

477 

537 

596 

657 

716 

776 

34 

449 

506 

561 

618 

674 

730 

36 

424 

477 

531 

534 

637 

689 

38 

402 

453 

>503 

553 

603 

653 

40 

382 

430 

478 

525 

573 

621 

42 

364 

409 

455 

500 

546 

591 

44 

347 

391 

434 

477 

521 

564 

46 

332 

374 

415 

456 

498 

539 

48 

318 

358 

397 

438 

477 

517 

50 

306 

344 

383 

420 

459 

497 

52 

294 

331 

369 

404 

441 

487 

54 

283 

318 

354 

389 

425 

459 

56 

273 

307 

341 

366 

410 

443 

58 

264 

296 

330 

354 

396 

428 

60 

255 

277 

319 

350 

383 

414 


low as 4500 feet per minute may give good results, wheel speed does 
not in general practice vary much from the ‘5500 feet given. Table 
XI gives wheel speeds used in good practice. 

Wheel Traverse. This is taken as the distance the abrasive 
wheel travels axially during a complete revolution of the work. 
While experts differ as to what proportion of the face of the wheel 
this should be, it would appear that where operating conditions 
will stand it, a traverse of above one-half the wheel face width per 
work revolution is desirable when rough grinding work. Fig. 326 
shows the traverse markings upon a piece of ground work. 


286 



















MACHINE SHOP WORK 


273 


Grinding Allowances. When in grinding practice the work 
has been previously rough turned, it is customary to leave an amount 
of stock to be removed in the grinding machine dependent upon 
the size and character of the work and upon the roughing out method 
employed. 

Table XII gives allowances left for grinding as worked out by 
the Landis Tool Company. If the roughing out is done, using an 
exceptionally coarse feed, as shown in Fig. 327, the tabulated allow- 



Fig. 327. Roughing-Out for Grinding Showing Heavy Cut 


ances will need to be exceeded. It is well to note here that tab¬ 
ulated grinding details in machine construction are useful chiefly 
as a starting basis. 

Abrasive Wheels. Large enterprises are devoted to the pro¬ 
duction of artificial abrasives. Increased knowledge in the man¬ 
ufacture of the wheels themselves and an added knowledge in wheel 
selection has materially changed the abrasive wheel industry from 
that of previous years. The greater portion of modern machine 
grinding is now done with the manufactured abrasives. These 
are in most part very efficient in cutting qualities and are sold under 
a variety of trade names such as tilv/ndum , aloxite , carborundum t 


287 













274 


MACHINE SHOP WORK 


TABLE XII 

Allowances for Grinding* 








Length 

( in .) 





Diam¬ 

eter 

3 

6 

9 

12 

15 | 

18 

1 24 

30 

| 36 

42 1 

48 

( in .) 





Allowance 

( in .) 





i 

0.010 

0.010 

0.010 

0.010 

0.015 

0.015 

0.015 

0.020 

0.020 

0.020 

0.020 

1 

0.010 

0.010 

0.010 

0.010 

0.015 

0.015 

0.015 

0.020 

0.020 

0.020 

0.020 

\ 

0.010 

0.010 

0.010 

0.015 

0.015 

0.015 

0.015 

0.020 

0.020 

0.020 

0.020 

H 

0.010 

0.010 

0.015 

0.015 

0.015 

0.015 

0.015 

0.020 

0.020 

0.020 

0.020 


0.010 

0.015 

0.015 

0.015 

0.015 

0.015 

0.020 

0.020 

0.020 

0.020 

0.020 

2 

0.015 

0.015 

0.015 

0.015 

0.015 

0.020 

0.020 

0.020 

0.020 

0.020 

0.025 

21 

0.015 

0.015 

0.015 

0.015 

0.020 

0.020 

0.020 

0.020 

0.020 

0.025 

0.025 

2£ 

0.015 

0.015 

0.015 

0.020 

0.020 

0.020 

0.020 

0.020 

0.025 

0.025 

0.025 

3 

0.015 

0.015 

0.020 

0.020 

0.020 

0.020 

0.020 

0.025 

0.025 

0.025 

0.025 

3£ 

0.015 

0.020 

0.020 

0.020 

0.020 

0.020 

0.025 

0.025 

0.025 

0.025 

0.025 

4 

0.020 

0.020 

0.020 

0.020 

0.020 

0.025 

0.025 

0.025 

0.025 

0.025 

0.030 


0.020 

0.020 

0.020 

0.020 

0.025 

0.025 

0.025 

0.025 

0.025 

0.030 

0.030 

5 

0.020 

0.020 

0.020 

0.025 

0.025 

0.025 

0.025 

0.025 

0.030 

0.030 

0.030 

6 

0.020 

0.020 

0.025 

0.025 

0.025 

0.025 

0.025 

0.030 

0.030 

0.030 

0.030 

7 

0.020 

0.025 

0.025 

0.025 

0.025 

0.025 

0.030 

0.030 

0.030 

0.030 

0.030 

8 

0.025 

0.025 

0.025 

0.025 

0.025 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

9 

0.025 

0.025 

0.025 

0.025 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

10 

0.025 

0.025 

0.025 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

11 

0.025 

0.025 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

12 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 


crystolon, and several others. Abrasive wheels can be had also in 
a variety of degrees of hardness, coarseness, and varying bonds, as 
is seen by consulting Tables XIII and XIV. Degrees of hardness, 
coarseness, and bonding condition make up what is known as the 
“grain” and the “grade” of the abrasive wheel. 

Grinding Methods. Skilled Operators. The larger manufac¬ 
turers of grinding machines have representatives trained to the 
highest skill in operating their line of machines. A purchaser of 
their machines can have one of these highly skilled operators demon¬ 
strate the maximum efficiency possibilities of the particular machine. 

Grinding Crank Shafts. As a sample of high speed grinding 
production the finishing of automobile crank shafts may be taken. 
Fig. 328 shows the methods employed. 

Flat Face Grinding. While the work illustrated in Fig. 325 is 
done by axially traversing a wheel having a face width of about 
two inches, an increasing amount of work is being done, using the 
wheel as a broad cutting tool and feeding the wheel directly into the 

* From Landis Tool Company, Waynesboro, Pennsylvania. 


288 




















MACHINE SHOP WORK 


275 


work until the desired diameter is obtained. By this method there 
is no axial traversing of the wheel while in its cut. Cup wheels 
having a width of face as great as nine inches have been used on 
such machines as shown in Fig. 329. By means of suitable face 



forming attachments, the face of the wheel can be surfaced to a 
variety of contours. It will therefore be seen that the new method 
of grinding can be employed not only for straight cylindrical sur¬ 
faces, but for work having an irregular contour. Fig. 330 shows 


289 


Fig. 328. Norton Grinding Machine Grinding Crank Shaft 
Courtesy of Norton Grinding Company, Worcester, Massachusetts 














276 MACHINE SHOP WORK 

TABLE XIII 
Norton Grade List 

The following grade list is used to designate the degree of hard¬ 
ness of vitrified and silicate wheels, both alundum and crystolon: 

E.Soft 

F 

G 

H 

I.Medium Soft 

J 

K 

L 

MEDIUM.M.MEDIUM 

N 

O 

P 

Medium Hard.Q 

R 

S 

T 

Hard..U 

V 

w 

X 

Extremely Hard.Y 

Z 

The intermediate letters between those designated as soft, medium soft, 
etc., indicate so many degrees harder or softer; e.g., L is one grade or degree 
softer than medium; 0, two degrees harder than medium, but not quite medium 
hard. 

Elastic wheels are graded as follows: 1 , 1\, 2 , #§, S } 4, 5, and 6. Grade 1 
is the softest and grade 6, the hardest. 

the correct form of work-supporting rests. Figs. 331, 332, and 
333 show how the wheel approaches the work for straight and for 
contour work. 

Internal Cylindrical Grinding . Machine grinding the internal 
surfaces of gas engine cylinders may be used as a good example of 
this line of production work. Figs. 334 and 335 show two views 
of such work. It will be noted that these views illustrate one of 
several special internal grinding machines particularly designed 
for this class of work. The prominent feature in its design is that 
in place of rotating the work against the grinding wheel, the work 
is rigidly held in a fixed position. By means of a slow revolving 


290 









Fig. 329. Norton Grinder with 5i-Inch Face Wheel for Grinding Ford 
Axles and Drive Shafts 



Fig. 330. Work Properly Supported 
Courtesy of Norton Grinding Company, 
Worcester, Massachusetts 


Figs 331 and 332. Set-Up for Grinding 
Straight and Contour Work with 
Norton Grinder 

Courtesy of "Machinery ", New York City 


291 















278 


MACHINE SHOP WORK 


TABLE XIV 

Selection of Grades 


Class of Work 

Alundum 

Crystolon 

Grain 

Grade 

Grain 

Grade 

Aluminum castings 

30 to 46 

3 to 4 Elas. 

20 to 24 

P to R 

Brass or bronze castings (large) 



20 to 24 

Q to R 

Brass or bronze castings (small) 



24 to 36 

P to R 

Brick, fire 



16 to 20 

P to Q 

Brick, pressed 



16 to 20 

O to P 

Car wheels, east iron 

• 


16 to 24 

P to Q 

Car wheels, chilled 

20 

Q 

16 to 24 

O to Q 

Cast iron, cylindrical 

24 comb. 

J to Iv 

30 to 46 

J to L 

Cast iron, surfacing 

20 to 46 

II to K 

16 to 30 

J to L 

Cast iron (small) castings 

24 to 30 

P to R 

20 to 30 

Q to S 

Cast iron (large) castings 

16 to 20 

Q to R 

16 to 24 

Q to S 

Chilled iron castings 

20 to 30 

P to U 

20 to 30 

Q 

Dies, chilled iron 



20 to 30 

O to Q 

Dies, st.eel 

36 to 60 

J to L 



Drop forging3 

20 to 30 

P to R 



TTanfirpers, east steel 

30 

P 



Hollowware, inside grinding 


30 

Q 

Hollowware, thin edges 



24 

U 

Internal grinding of automobile cylinders 





(cast iron) 



30 to 60 

1 to L 

Internal grinding, hardened steel 

46 t,o 60 

J to M 



Knives (paper), automatic grinding 

36 to 46 

J to K 



Knives (planer), automatic grinding 

30 to 46 

J to K 



Knives, leather shaving ' 

60 

N to O 



Knives, leather splitting 

24 to 30 

1 to 2 Elas. 



Knives, molding bits, etc. 

f 46 to 60 

3 Elas. 



\46 to 60 

M 



Knives (planing mill), hand grinding 

46 to 60 

J to M 



Knives, shear and shear blades 

30 to 60 

J to M 



Knives, shoe 

60 

M 



Lathe centers 

46 to 120 

J to M 



Lathe and planer tools 

(20 to 24 

P Sil. 



\20 to 36 

O to P 



Machine shop use, general 

20 to 36 

O to Q 



Malleable iron castings (large) 

14 to 20 

P to U 

16 to 20 

R to S 

Malleable iron castings (small) 

20 to 30 

P to R 

20 to 30 

Q to S 

Marble, finishing 



150 to F 

M 

Marble, roughing 


. 

16 to 46 

M 

Marble, coping 



36 to 46 

O to S 

Marble, molding 



4 

o 

Milling cutters, automatic or semi-auto- 





matic grinding 

46 to 60 

H to M 



Milling cutters, hand grinding 

46 to 60 

J to M 



Nickel castings 

20 to 24 

P to Q 

20 to 24 

R 

Pearl grinding, roughing 



30 to 50 

P to U 

Pearl grinding, finishing 



100 to 150 

M t,o P 

Plow bodies (cast iron), surfacing 



24 

R 

Plows (steel), jointing 

20 to 24 

It to S 



Plow points (chilled iron), surfacing 



20 to 30 

Q to S 

Plows (steel), surfacing 

16 to 24 

Q to S 


Porcelain, roughing 


36 to 50 

O to R 

Pulleys (e i), surfacing faces of 



30 to 36 

K to L 

Radiators (cast iron), edges of 



24 to 30 

R. t.o 

Razors, grinding and concaving 

46 to 120 

II to O 



Reamers, taps, milling cutters, etc., hand 





grinding 

46 to 60 

K to O 




292 







































































































MACHINE SHOP WORK 


279 


TABLE XIV—(Continued) 


Selection of Grades 



Alundtjm 

Crystolon 

Class of Work 

Grain 

Grade 

Grain 

Grade 

Reamers, taps, milling cutters, etc., special 





machines 

Rolls (cast iron), wet 

46 to 60 
24 to 36 

J to M 

J to M 

24 to 36 

j to M 

Rolls (chilled iron), finishings 

Rolls (chilled iron), roughing 

Rubber 

70 

l£ to 2 Elas. 

70 to 80 

l£ to 2 Elas. 

30 to 50 

J to K 

30 to 46 
30 to 50 

2 to 3 Elas. 
Kto M 

Sad irons, finishing 



80 to 120 

Q to R 

Sad irons, roughing 



20 to 30 

Q to S 

Saws, gumming and sharpening 

36 to 50 

M to N 



Saws, cold cutting-off 

60 

O to Q 



Shovels, edging 

24 

Q „ 



Spiral springs, ends of 

16 to 20 

Q to R 



Steel (soft), cylindrical grinding 

(24 comb. 
(46 to 60 
24 to 36 

L to N 

• » . . 


Steel (soft), surface grinding 

L to N 

H to K 



Steel (hardened), cylindrical grinding 

/24 comb. 

K 



Steel (hardened), surface grinding 

(46 to 60 
36 to 46 

J to L 

H to K 



Steel, large castings 

12 to 20 

Q to U 



Steel, small castings 

20 to 30 

P to R 

. 


Steel (manganese), safe work 

16 to 46 

L to P 



Steel (manganese), frogs and switches 

14 to 16 

Q to U 

*•••*•• V* 

. 

Structural steel 

16 to 24 

P to R 

20 Vo 36 

Q to R 

Stove castings 

20 to 36 

P to Q 

Twist drills, hand grinding 

46 to 60 

M 



Twist drills, special machines 

36 to 60 

K to M 



Wagon springs, ends of 

Wire, ends of steel 

20 to 30 

P to R 



36 to 80 

Q to R 

. 


Wrought iron 

Woodworking tools 

12 to 30 
46 to 60 

P to U 

K to M 




motion given to the spindle carrying frame, the highly speeded 
rotating wheel carrying spindle is itself carried about in a circle. 
Provisional adjustments can be made to alter the diameter of this 
circle to meet changes in the cylinder dimensions. When water 
jacketed work is being ground, means are provided for circulating 
water through the jacket, the grinding wheel itself in this case 
working dry. Suitable wheel speeds and traverse feeds are provided 
for the range of work the machine is designed to cover. Fig. 336 
shows operation of grinding wrist-pin bearing, while Fig. 337 illus¬ 
trates charging the grinding jig. 

Flat Surface Grinding . Under this heading properly comes 
those machines designed for intensive production. These are of two 
distinct types. The one shown in Fig. 338 carries a wheel that 
approaches the work radially, while that shown in Fig. 339 uses the 
side of a cup-shaped wheel in contact with the work. By means of 


293 























































280 


MACHINE SHOP WORK 


powerful wheel driving belts and rapid table traverse, these machines 
produce flat surfaces with an efficiency and accuracy that leaves 
little to be desired. The work as shown is held upon magnetic 
chucks and the throw of a simple switch clamps or unclamps it. 
In use the wheel and the work are flooded with a suitable cutting 
lubricant. In Fig. 340 are shown a number of gun parts finished 



Fig. 333. Diagram of Set-Ups Shown in Figs. 331 and 332 
Courtesy of “ Machinery ", New York City 


A 

Work:— Main drive gear, 0.20 per cent carbon alloy steel, carbonized and 
heat-treated. 

Operation: —Straight-in grinding external diameter with a Norton (vitrified) 
alundum combination wheel, grain 38-24, grade L; 20 inches diameter, 4-inch 
lace; speed, 1241 r.p.m. 6500 feet surface speed; work speed, about 100 
r.p.m.—41 feet surface speed; amount removed from diameter, 0.010 inch. 

Remarks:— Wide-face wheel is fed straight in on portions (a) and (b), not 
traversed; small end (c) is also ground in same setting by shifting wheel; pro¬ 
duction, 26o pieces in nine hours; machine used, 10 by 36 inch Norton plain grind¬ 
ing machine. 


B 

and lSdeneid Idler gGar shaft '°- 20 P er cent carbon open-hearth steel, carbonized 

, .. Operation:— Straight-in grinding two external diameters with a Norton 
(vitrified) alundum combination wheel, grain 38-24, grade L; 20 inches diameter, 
6-inch face, speed 1241 r.p.m.—6500 feet surface speed; work speed, 100 
inch 11 lGet SU “ ace s P eec *i amount removed from diameter 0.015 to 0.025 

. Remarks:— Wide-f ace wheel is fed straight in on work, not traversed- 50 
pieces turned out to each truing of wheel; production, 375 pieces in nine hours- 
machine used, 10 by 36 inch Norton plain grinding machine 


294 



















































































MACHINE SHOP WORK 


281 



Fig. 334. Grinding Gas Engine Cylinders. View Shows Exhaust for Dust, Jig for Holding 
Cylinders, and Eccentric Wheel Spindle 
Courtesy of Heald Machine Company, Worcester, Massachusetts 



Fig. 335. Grinding Gas Engine Cylinders. Same Set-Up as Fig. 331, Showing Holding Jig 
and Turning Tool at Mouth of Hole 


by a vertical grinder, removing .005 inch to .010 inch of stock. 
Table XV shows the number of pieces produced per hour. 


295 








282 


MACHINE SHOP WORK 



296 


Fig. 336. Set-Up for Grinding Wrist-Pin Bearing; Grinding Time 3 Minutes per Piston 
Courtesy of Eeald Machine Company, Worcester, Massachusetts 













Fig. 337. Charging Grinding Jig Shown in Fig. 336 



Fig. 338. Example of Flat Surface Grinding 
Courtesy of Norton Grinding Company, Worcester, Massachusetts 


297 








284 


MACHINE SHOP WORK 


Rate of 


No 

1 

on 

No. 

2 

on 

No. 

3 

on 

No. 

4 

on 

No. 

5 

on 

No. 

6 

on 

No. 

7 

on 

No. 

8 

on 

No. 

9 

on 

No. 

10 

on 

No. 

11 

on 

No. 

12 

on 


TABLE ) 
Grinding Gun Parts 

— 40 to 50 per hour 
-125 per hour 
-175 per hour 
-100 per hour 
-150 per hour 
-150 per hour 
-175 per hour 
-200 per hour 
-200 per hour 
-200 per hour 
-250 per hour 


TABLE XV 

on Vertical Grinder 

No. 13 on two sides—175 per hour 
No. 14 on two sides—200 per hour 
No. 15 on two sides—200 per hour 
No. 16 on two sides—175 per hour 
No. 17 on two sides—100 per hour 
No. 18 on two sides—125 per hour 
No. 19 on two sides—200 per hour 
No. 20 on two sides—150 per hour 
No. 21 on two sides—150 per hour 
No. 22 on two sides—100 per hour 
No. 23 on two sides—150 per hour 



Fig. 339. Pratt and Whitney Grinding Machine Using Magnetic Flat Chuck 


298 










MACHINE SHOP WORK 


285 



Fig. 340. Gun Parts Ground on Vertical Grinder 

MILLING MACHINES 

Production milling is done on three distinct types of machines 
known as the horizontal, the vertical, and the planer type. 

Horizontal Milling Machine. Fig. 341 shows a representative 
machine of this type. Designed and used as shown, this machine 
is capable of very rapid production. The prominent features are 
its weight and the size of its working parts, its large bearing surfaces, 
its all geared driving speed changes, its all geared feeds, and the 
yoking of the knee to the outer end of the cutter arbor. 

Vertical Milling Machine. Fig. 342 is a representative machine 
of this type. While side milling can be done on this type of machine, 
its use is very largely confined to the use of end and face cutting. 
In common with all high production machines, it has weight, 
generous bearing surfaces, large table capacity, great driving power, 
and a possibility for coarse feeding. 

Planer Milling Machine. The planer type of milling machine 
is the most massive and the heavier machine of the three types. 


299 


























































286 MACHINE SHOP WORK 

A typical machine is shown in Fig. 343. It will be noted that by 
using side head spindles in conjunction with horizontal gangs of 
cutters, three or more surfaces may be worked upon simultaneously. 

Production Cutters. It is evident that the cutter equipment 
must be equal to the possibilities of the machine if its capacity 
production is maintained. Fig. 344 is a characteristic cutter used 
in a horizontal milling machine. Note the large axial hole, making 


Fig. 341. Horizontal Milling Machine with Work in Process 
Courtesy of Cincinnati Milling Machine Company, Cincinnati , Ohio 

possible the use of rigid arbors, the greatly increased spacing of the 
teeth, and the increaaed cutting rake given by undercutting. Fig. 345 
shows the usual type of cutter used when heavy slabbing cuts are 
taken in a vertical machine. The characteristics of coarse tooth 
pitch, increased cutting rake, and rigidity of attachment are prom¬ 
inent in this cutter. Either or both of these types of cutter are used 
on all three types of machine. Fig. 346 shows an inserted tooth 
gang of Ingersoll production cutters in actual operation. 


300 











Fig. 342. Vertical Milling Machine in Action. Work-Holding Fixture Rotates 
at Rate of 10 Inches per Minute; Production 195 Yokes per Hour 
Courtesy of Horizontal Milling Machine Company, Hyde Park, Massachusetts 

conveniently the work is held directly upon the work table. Mag¬ 
netic chucks are used to hold thin work. 

Cutting Speeds. These must be proportioned to the materials 
being milled, their relative hardness, the depth of cut, and the amount 
the tool can be fed. 


MACHINE SHOP WORK 287 


Work Holding. This problem is usually cared for by special 
work-holding devices termed “fixtures”. These fixtures are con¬ 
structed to grip and support the work so that the pressures and 
thrusts of cutting are cared for. The fixtures themselves are bolted 
directly to the work table. Where it can be done quickly and 


301 







288 


MACHINE SHOP WORK 



Fig. 343. Ingersoll Horizontal Milling Machine, Milling Gasoline Traction Engine Frame? 
Courtesy of International Harvester Company, Chicago 



302 












Fig. 345. High-Power Face Mill with High-Speed Steel Teeth 
Courtesy of Union Twist Drill Company , Athol, Massachusetts 



Fig. 346. Production Milling Cutter in Heavy Work 
Courtesy of Ingersoll Milling Machine Company, Rockford, Illinois 


303 




290 


MACHINE SHOP WORK 



Cutting Feeds. These also vary with working conditions. 
The coarsest practical feed is usually found by experiment and 
maintained, bringing the cutter speed up to meet it. 

Tool Lubrication. Cast iron is about the only material milled 
which is cut “dry”. In milling other metals and alloys a copious 
supply of some cutting lubricant is used. This is pumped to the 
tool in quantities sufficient to flood not only the cutter but to a large 
extent the work. This is well shown in Fig. 347 where the cutters 
are working on steel. 

DRILLING MACHINES 

Production drilling machines are of two sorts: Those designed 
for heavy drilling, and those for the lighter jobs. 


Fig. 347. Ingersoll Horizontal Miller Doing Heavy Grinding 
Note how lubricant floods the work in milling steel 

Heavy High=Speed Drillers. Fig. 348 is fairly representative 
of the type designed to use high-speed steel drills of the larger 
sizes to their full capacity. The frame or post of this machine 
is of a form similar to the frame of a punch or shear press. Pressure 
tests on a drill of l|-inch diameter, given a feed of 0.030 inch per 
revolution, have recorded a total load pressure of nearly three tons. 
From this it will be seen why the frame is made as shown. Feeds 
much in excess of 0.030 inch can be obtained in this machine. Use 
the coarsest feed practicable and balance the speed of cutting to it. 


304 







MACHINE SHOP WORK 


291 




Light High=Speed Drillers. In the lighter jobs of drilling, a 
feed exceeding 0.015 inch per revolution is seldom used. Rapid 
production is gained in this case by maintaining a high cutting 
speed. Tables XVI and XVII, published by the Henry and Wright 
Company, show certain drilling practice where the feed does not 



Fi". 348. Baker Driller Driving 24-Inch Drill through Drop-Forged 
Wrought-Iron Saddles 
Courtesy of Baker Brothers, Toledo, Ohio 


exceed 0.01G inch per revolution. Fig. 349 shows a power feed, 
four-spindle high-speed driller. In designing this machine every¬ 
thing has been done to render its operation rapid and efficient. 

Special Drillers. There are many of these, some of which are 
very complicated. Fig. 350 shows a machine designed for the single 


305 





292 


MACHINE SHOP WORK 



Fig. 349. Four-Spindle High-Speed Ball-Bearing Sensitive Driller 
Courtesy of Washburn Shops, Worcester, Massachusetts 

purpose of drilling the clearance holes in threading dies. By using 
four spindles and suitable work-holding table chucks, a die is com¬ 
pleted for each stroke of the table. 

Production Figures. While there are many records of high 
production drilling, due to the great variety of drill work, it is 
impossible to give a table to meet all needs. 


306 
















MACHINE SHOP WORK 


293 


TABLE XVI 


Carbon=Steel Drills 


Size 

Feed 

Bronze 

C. Iron 

Hard 

Mild 

Drop 

Mal. 

Tool 

Cast 

of 

per 

Brass 

Ann’ld 

C. Iron 

Steel 

Forg. 

Iron 

Steel 

Steel 

Drill 

Rev. 

150 Ft. 

85 Ft. 

40 Ft. 

60 Ft. 

30 Ft. 

45 Ft. 

30 Ft. 

20 Ft. 

(in.) 

(in.) 

r.p.m. 

r.p.m. 

r.p.m. 

r.p.m. 

r.p.m. 

r.p.m. 

r.p.m. 

r.p.m. 

1 

16 

.003 


5185 

2440 

3660 

1830 

2745 

1830 

1220 

1 

8 

.004 

4575 

2593 

1220 

1830 

915 

1375 

915 

610 

& 

.005 

3050 

1728 

813 

1220 

610 

915 

610 

407 

1 

4 

.006 

2287 

1296 

610 

915 

458 

636 

458 

305 

5 

16 

.007 

1830 

1037 

488 

732 

366 

569 

366 

245 

3 

8 

.008 

1525 

864 

407 

610 

305 

458 

305 

203 

7 

16 

.009 

1307 

741 

349 

523 

261 

392 

261 

174 

1 

2 

.010 

1143 

648 

305 

458 

229 

343 

229 

153 

5 

8 

.011 

915 

519 

244 

366 

183 

275 

183 

122 

3 

4 

.012 

762 

432 

204 

305 

153 

212 

153 

102 

7 

8 

.013 

654 

371 

175 

262 

131 

196 

131 

87 

1 

.014 

571 

323 

153 

229 

115 

172 

115 

77 

li 

.016 

458 

260 

122 

183 

92 

138 

92 

61 

li 

.016 

381 

216 

102 

153 

77 

106 

77 

51 

If 

.016 

327 

186 

88 

131 

66 

98 

66 

44 

2 

.016 

286 

162 

87 

115 

58 

86 

58 

39 


TABLE XVII 


High=Speed Drills 


Size 

of 

Drill 

(in.) 

Feed 

per 

Rev. 

(in.) 

Bronze 
Brass 
300 FT. 
r.p.m. 

C.Iron 
Ann’ld 
170 FT. 
r.p.m. 

C. Iron 
Hard 

80 FT. 
r.p.m. 

Mild 
Steel 
120 FT. 
r.p.m. 

Drop 

Forg. 

60 FT. 
r.p.m. 

Mal. 

Iron 

90 FT. 
r.p.m. 

Tool 
Steel 
60 FT. 
r.p.m. 

Cast 
Steel 
40 FT. 
r.p.m. 

Te 

.003 



4880 


3660 


3660 

2440 

i 

.004 


5185 

2440 

3660 

1830 

2745 

1830 

1220 

_3_ 

1 6 

.005 


3456 

1626 

2440 

1210 

1830 

1220 

807 

1 

4 

.006 

4575 

2593 

1220 

1830 

915 

1375 

915 

610 

_5_ 

1 6 

.007 

3660 

2074 

976 

1464 

732 

1138 

732 

490 

3 

s 

.008 

3050 

1728 

813 

1220 

610 

915 

610 

407 


.009 

2614 

1482 

698 

1046 

522 

784 

522 

348 

h 

.010 

2287 

1296 

610 

915 

458 

636 

458 

305 

5 

8 

.011 

1830 

1037 

488 

732 

366 

569 

366 

245 

3 

4 

.012 

1525 

864 

407 

610 

305 

458 

• 305 

203 

| 

.013 

1307 

741 

349 

523 

261 

392 

261 

174 

1 

.014 

1143 

648 

305 

458 

229 

349 

229 

153 

H 

.016 

915 

519 

244 

366 

183 

275 

183 

122 

n 

.016 

762 

432 

204 

305 

153 

212 

153 

102 

if 

.016 

654 

371 

175 

262 

131 

196 

131 

87 

2 

.016 

571 

323 

153 

229 

115 

172 

115 

77 


Work Holding. This is usually accomplished by work-holding 
jigs. These may be held loosely upon the work table or rigidly 
fastened to it as their use may warrant. (See “ Jig-Making”.) 


307 






































294 


MACHINE SHOP WORK 


Lubrication. Flood lubrication of the drill and the work is 
usual when production drilling upon metals other than cast iron, 



Fig. 350. “Single Purpose” Bemis Driller 


and tanks, pumps, and a circulating system of pipes and nozzles are 
provided on all drilling machines when desired for this purpose. 


308 









MACHINE SHOP WORK 


295 



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309 


Fig. 351. “Reed” Geared-Drive and Geared-Feed Production Lathe 
Courtesy of Reed-Prentice Company , Worcester, Massachusetts 



































296 


MACHINE SHOP WORK 



TURNING MACHINES 

Special and specialized machines for high speed turning will 
be illustrated under this heading. 

Turning Lathe. Fig. 351 shows a production lathe for rapid 
turning of machine parts. It is representative of its class. This 
machine has all-geared drive, all-geared feed, and is capable of 
removing, when properly operated, several pounds of material per 
minute from such materials as chrome nickel steel. Its specialized 


characteristics are coarse feeds, powerful driving capacity, and conven¬ 
ience of operation. Fig. 352 is a transparent view of the geared feed. 

Vertical Type. Fig. 353 shows a type of turning machine 
in which the work is mounted upon a rotating horizontal work 
table. The advantages of this type for certain classes of work can 
be readily seen. The tool holding heads are carried upon slides 
and can be fed both vertically and horizontally. Boring, turning, 
facing, and threading can be done on this machine. Its massive 
construction and ease of operation render it a rapid producer. 
Fig. 354 shows the machine on some characteristic work. 


Fig. 352. Tiansparent View of “Reed” Quick-Change Gear Mechanism 


310 










MACHINE SHOP WORK 


297 


Turret Type. Where several turning operations are to be 
performed upon bar stock or upon work held in a chuck, recourse 
is often made to the use of a tool-holding turret. Fig. 355 shows 



Fig. 353. Bullard Vertical Turret Lathe 
Courtesy of Bullard Machine Tool Company, Bridgeport, Connecticut 


a horizontal turret machine for making machine parts from bar 
stock. The cutting tools are fitted with shanks suitable for holding 
them in the turret, and the cutting principle is the same as in all 


311 











298 


MACHINE SHOP WORK 



Fig. 35 1 . Three Views of Bullard Turret Lathe in Action 
Courtesy of “ Machinery", New York City 



cutting tools. Both long and 
short turning can be done in this 
machine. The turret provides for 
six tools. 

Fig. 356 shows a similar ma¬ 
chine designed to handle iron 
or steel castings. This machine 
when properly tooled up, will 
perform turning and boring 



Fig. 355a Diagram Showing Piece Producted 
by Turret Lathe, Fig.. 355b 


312 


































MACHINE SHOP WORK 


299 



313 


Fig. 355b. Jones and Lamson “Hartness” Turret Lathe Finishing Bar Work 

Courtesy of “Machinery ” f New York City 



























300 


MACHINE SHOP WORK 



314 


Fig. 356. Hartness Turret Lathe Operating on Chuck Parts. Chasing Attachment and Long Boring Bar in Use 

Courtesy of Jones and Lamson Machine Company , Springfield f Vermont 


























MACHINE SHOP WORK 


301 



- 




m iVi 








315 


Fig. 357. “Lo-Swing” Turning Machine with Work in Progress 
Courtesy of Fitchburg Machine Works, Fitchburg, Massachusetts 


































‘-Wtf M °u°S uon~*do vi 


302 


MACHINE SHOP WORK 





316 


Fig. 353. Illustration of Typical Job of Spindle Turning with Time Taken for Work 




























































































































































MACHINE SHOP WORK 


303 


operations upon a large variety of parts. The fundamental cutting 
principle is maintained in its tooling. It is an efficient producer. 

“Lo-Swing” Type . Fig. 357 shows a highly specialized turning 
machine in which a train of cutting tools may be operated. Rough¬ 
ing out spindles is a particular function of this machine. Fig. 358 
illustrates a typical “lo-swing” job. 

Lubrication. All production turning machines may be, when 
desired, equipped with a lubrication system to flood the cutting 
tool with either oil or compound. 

Cutting Speeds and Feeds. All these machines are designed 
to work any cutting tool to the limit of its endurance. 



Fig. 359. Cleveland Automatic 

Courtesy of Cleveland Automatic Machine Company, Cleveland, Ohio 

Automatics. The term “automatic” designates a line of 
machines, in which, when once properly tooled and adjusted, the 
functions of the machine are to a considerable extent automatic 
in their action. By means of cam movements, and link and 
crank motions, the cutting tools and the work are made to func¬ 
tion as desired. In Figs. 359, 360, and 361 are shown representa¬ 
tive automatics. 

Uses of Automatics. The broadest use of such machines is 
upon work which, besides being turned, is also drilled and perhaps 
threaded. The automatic shown in Fig. 359 is for heavy w r ork and 
takes through its work spindle, bar stock several inches in diameter. 
The bar is worked upon by both turret and cross-slide cutting tools. 


317 

















304 


MACHINE SHOP WORK 


The tool turret is fed by a cylindrical cam grooved to give a powerful 
feed. The machine can be functioned to complete a piece in one 
cycle of the machine. As the finished part is dropped,, the work 
bar is automatically advanced to receive another tooling, and goes 
through the same cycle of operations. 

Fig. 360 is representative of a type of machine used in turning 
and boring special castings. Like other automatics the cutting 
tools are held in turrets, and are automatically rotated into position 
and advanced by cam movements. 



Fig. 360. Typical Automatic Turning and Boring Special Castings 

Fig. 361 shows a machine used largely in producing the smaller 
machine parts, as, for example, the smaller screws, studs, collars, 
sleeves, etc., used in machine construction. 

The automatic shown in Fig. 362 is designed for producing 
work similar to that produced by the machine, Fig. 361. It, how¬ 
ever, is provided with five work spindles. The five feed tubes are 
shown at the left. 

Lubrication. Automatics such as those shown are provided 
with stream or flood lubrication systems. 


3X8 





MACHINE SHOP WORK 


305 



319 


Fig. 361. Automatic at Work on Hollow Cylindrical Sleeves 
Courtesy of Brown and Sharpe Manufacturing Company, Providence, Rhode Island 














306 


MACHINE SHOP WORK 



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ll 

a s 


a> 

r i 

o 

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a s 
« ^ 
T5 

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A 1 


i 

© 


PLANING MACHINES 

Production Planers. The machine tool shown in Fig. 363 is for 
quantity production of plane surfaces. Enormous machines of this 
type are in use, constructed to drive and feed the best of cutting tools 


320 











MACHINE SHOP WORK 307 

to their endurance limits. By the use of several tool-carrying heads 
tooling can be done on the top and the side surfaces simultaneously. 


Work Holding. In the case of production work, where size 
precludes the mounting of more than a single piece on the 


321 


Fig. 363. Cincinnati Planer with Four Tools Cutting 
Courtesy of Cincinnati Planer Company, Cincinnati, Ohio 







308 


MACHINE SHOP WORK 


work table, the work usually rests on the table itself without sup¬ 
porting fixtures. In locating the work and holding it true to its 



location, a variety of bolts, straps, thrust blocks, angle irons, and 
struts are usually available. Where the size of the work warrants 


322 






MACHINE SHOP WORK 


309 


mounting more than a single piece upon the work table, work-holding 
fixtures, as shown in Fig. 364, are usually provided. These may 
also, by design, accurately locate the pieces. 

Lubrication. In planer work, the cutting tool is seldom lubri¬ 
cated. 

BROACHING MACHINES 

Types of Machines and Nature of Work. Fig. 365 is repre¬ 
sentative of a type of machine tool which makes use of a train of 



Fig. 365. Typical Broaching Machine 
Courtesy of LaPointe Machine Tool Company, Hudson, Massachusetts 

cutting edges for roughing and finishing holes in machine parts. 
Typical broaches are shown in Fig. 366. The cutting edges are 
usually formed as an integral part of the broach itself. 

Operation . The leading end of the broach is passed through 
the previously drilled or cored hole in the piece of work, and is 
attached to the power or work spindle. This spindle, as shown in 


323 













310 


MACHINE SHOP WORK 



Fig. 366. Typical Broaches 

Courtesy of LaPointe Machine Tool Company, Hudson, Massachusetts 


Fig. 365, is a threaded bar running in a suitable frame. The driving 
mechanism screws the threaded spindle along the axis of the machine 
until the broach has been pulled through the hole in the work. 

Work Holding . The work is held against a footing block which 
resists the thrust due to the pull of the broach. 

Lubrication. As the speed of cutting is comparatively slow, the 
cutting lubricant may be applied with a brush or by use of a drip can. 

Production. Holes having other than a circular form are 
.the particular province of the broaching machine. Fig. 367 shows 
some typical holes and Table XVIII gives rates of production. 

TABLE XVIII 

Data on Rates of Production with Different Broaching Machines* 

Note. Numbers refer to Fig. 367. 

No. 1. Hexagon Hole with One Round Side. Distance across flats 
If in., length 1§ in., material steel. No. 2 Machine. Production 45 pieces per 
hour. 

* Courtesy of LaPointe Machine Tool Company, Hudson, Massachusetts. 


324 






























MACHINE SHOP WORK 


311 


No. 2. Four Splines. Hole 1| in. diameter, splines | in. X n in., 
21 in. long, material steel. No. 3 Machine. Production 20 pieces per hour. 

No. 3. Square Hole. Distance across flats 1 in., 11 in. long, material 
steel. No. 2 Machine. Production 40 pieces per hour. 

No. 4. Four Spiral Keys. Diameter of hole 1 in., keys 1 in. X I in., 

2 in. long, material steel. No. 3 Machine. Production 15 pieces per hour. 

No. 5. Clutch Used on Mining Machinery. Diameter of hole 21 in. 
Double depth of slots 3f in., length 2 in., material steel. No. 3 Machine. Pro¬ 
duction 20 pieces per hour. 

No. 6. Solid Key. Taken from 11 in. round hole, leaving solid key 
| in. X 1 in-, length 21 in., material steel. No. 3 Machine. Production 15 
pieces per hour. 

No. 7. Six Radial Splines. Diameter of hole 21 in., splines f in. X 1 in., 
2g in. long, material steel. No. 3 Machine. Production 20 pieces per hour. 

No. 8. Housing for Bronze Bearings. Openings 4! in. X 11 in., 2 in. 
through, material C. I. No. 3 Machine. Production from rough casting 20 
pieces per hour. 

No. 9. Square Hole. Distance across flats 2 in., length 31 in., material 
steel. No. 3 Machine. Production from a drilled hole, 15 pieces per hour. 

No. 10. Square Hole. Distance across flats 3 in., length 4 in., material 
steel. No. 4 Machine. Production from drilled hole, 15 pieces per hour. 

No. 11. Three Dovetail Splines. Diameter of hole 1| in., splines 
1 in. X A in., ^ in. long, material brass. No. 3 Machine. Production 45 pieces 
per hour. 

No. 12. Eight Dovetail Splines. Diameter of hole 3f in., splines 
s i n< x A in., 3 in - long, material steel. No. 4 Machine. Production 15 pieces 

per hour. 

No. 13. Square Hole. If in. across flats, 5 in. long, material steel. 
No. 3 Machine. Production from drilled hole, 15 pieces per hour. 

No. 14. Universal Joint Part. Hole 2A in. across flats, | in. through, 
material C. I. No. 3 Machine. Production 30 pieces per hour. 

No. 15. Babbitt Bearing. Diameter 2 in., length 2\ in. Broached to 
exact size, compressed and burnished. No. 3 Machine. Production 60 pieces 
per hour. 

No. 16. Round Hole. 3 in. diameter, 4| in. long, material C. I. No. 3 
Machine. Production from cored hole 30 pieces per hour. 

No. 17. Cruciform Used in Mining Machinery. Splines § in. X f in., 
7 in. long, material steel. No. 3 Machine. Production from I in. round hole, 
7 pieces per hour. 

No. 18. Oval Shaped Holes. H in. X I in., \ in. through, material 
steel. No. 2 Machine. Production approximately 600 holes per hour. 

No 19. Revolver Frame. Size of hole for chamber Iff in. X 11 in., 
f in. through, material steel. No. 2 Machine. Production from rough forging 
20 pieces per hour. 

No. 20. Hexagon Hole. Distance across flats 2f in., 2g in. long, material 
steel. No. 3 Machine. Production from drilled hole 40 pieces per hour. 

No. 21. Two-Spline Hole. 1A in. X A in., 31 in. long, material steel. 
No. 2 Machine. Production from f in. drilled hole, 10 pieces per hour. 


325 







w: ; i’ : ; 


N UDSON. HASS , U.S.A 


Fig. 367. Sample of Broaching Work 
Courtesy of LaPointe Machine Tool Company, Hudson, Massachusetts 















MACHINE SHOP WORK 


313 


No. 22. Hole. f in. X te in., f in. long, material steel. No. 1 Machine. 
Production from drilled hole 25 pieces per hour. 

No. 23. Square Hole. f in. across flats, 2 in. long, material steel. No. 1 
Machine. Production from drilled hole 20 pieces per hour. 

No. 24. Pear Shaped Hole. Diameter of round broach 1 in., If in. long, 
material steel. No. 2 Machine. Production 20 pieces per hour. 

No. 25. Internal Gear. Hole If in., If in. long, 15 teeth, material 
steel. No. 3 Machine. Production from drilled hole 40 pieces per hour. 

No. 26. Internal Ratchet 140 Teeth. Diameter of hole 1 in., length 
If in., material steel. No. 2 Machine. Production 45 pieces per hour. 

No. 27. Six Splines. Diameter of hole 2| in., splines f in. X f in., 1 in. 
long, material drop-forged steel. No. 4 Machine. Production 35 pieces per hour. 

No. 28. Bronze Bushing. Hole If in. diameter, If in. long. No. 3 
Machine. Broached to exact size, compressed and burnished. Production 
from cored hole 100 pieces per hour. 

No. 29. Magneto Coupling. Hole If in. diameter, f in. long, 20 teeth, 
material steel. No. 3 Machine. Production from drilled hole 90 pieces per 

hour. 

No. 30. Two Spiral Keyways. Diameter of hole 2 in., keyways 
f in. X f in., If in. long, material steel. No. 3 Machine. Production 40 pieces 

per hour. 

No. 31. Ten Splines. Diameter of hole If in., splines f in. X f in., 
If in. long, material steel. No. 3 Machine. Production 45 pieces per hour. 

No. 32. Tool Steel Die for Pressing Tin Top on Bottles. Diameter 
of hole lrs in., f in. long, 21 teeth. No. 2 Machine. Production from drilled 
hole 60 pieces per hour. 

No. 33. Four Spline. Diameter of hole If in., splines ^ in. X f in. 
If in. long, material steel. No. 2 Machine. Production 45 pieces per hour. 

No. 34. Taper Square Hole. Distance across flats, small end, If in., 
large end If in., 2 in. long, material steel. No. 2 Machine. Production 12 
pieces per hour. 

No. 35. Four Solid Keys. Diameter of hole Iris in., keys ^ in. X f in., 
If in. long, material steel. No. 3 Machine. Production 20 pieces per hour. 

No. 36. Bushing for Trolley Wheel. Diameter of hole f in., six 
spiral keyways f in. X n in., If in. long, material bronze. No. 2 Machine. 
Production 100 pieces per hour. 

No. 37. Four Splines in Taper Hole. Hole f in. diameter at small 
end, f in. diameter at large end, splines f in. X re in., f in. long. Splines parallel 
with taper, material steel. No. 1 Machine. Production 25 pieces per hour. 

No. 38. Four Splines. Diameter of hole f in., splines f in. X f in., 
f in. long, material steel. No. 1 Machine. Production 15 pieces per hour. 

No. 39. Single Keyway. Diameter of hole f in., key way & in. X rs in., 
f in. long, material brass. No. 1 Machine. Production approximately 250 
pieces per hour. 

No. 40. Single Keyway. Diameter of hole f in., keyway & in. X -h in., 
1 in. long, material steel. No. 1 Machine. Production 160 pieces per hour. 


327 


314 


MACHINE SHOP WORK 


PRODUCTION TOOLS, JIGS, AND FIXTURES 
CUTTING TOOLS 

Materials. Iron. Iron is one of the commonest metals in 
use. In nature it is found in a form known as iron ore. In this 
form it has many impurities from which it must be separated before 
it is valuable as an article of commerce. By well-known methods 
commercially pure iron is obtained from the iron ore. Combining 
this commercially pure iron with other ingredients under well-known 
methods of heating, the various grades of steels are produced. 

Tool Steel. For generations cutting tools as used in machine 
shop practice have been made from that grade of steel commercially 
known as tool steel, the principal constituents of which are pure 
iron and carbon. In recent years, the metallurgist has combined 
other metals with iron to produce steels suitable for cutting tools, 
which have in many cases superseded the older grades of tool steel. 
To distinguish the older grades from the newer, the former are now 
generally termed carbon tool steels or simply carbon steels. In 
all the steels iron is the principal constituent. For example, carbon 
tool steel may have less than onfc per cent of carbon in its make-up 
and seldom has to exceed 1.250 per cent of carbon for ordinary 
shop cutting tools. In designating percentages of constituents, 
the steel-maker and user usually refers to them as so many “points”. 
For example, instead of saying that a certain steel has eighty hun¬ 
dredths of one per cent of carbon, he would say that the steel was 
eighty point carbon; this is usually written “80 point”. All tool 
steels have the peculiar quality of acquiring an intense hardness 
when heated to the requisite degree of temperature and then cooled 
> suddenly. If this is properly and scientifically done, a beautiful 
cutting quality results. The older carbon steel cutting tool has 
this weakness, however, that it loses its hardness at a comparatively 
low cutting temperature. As rapid metal cutting generates con¬ 
siderable quantities of heat, this tendency of the carbon steel cutting 
tool to lose its extreme hardness precludes rapid cutting and holds 
the operator to low cutting speeds. A glance at the accompanying 
speed tables clearly shows this. 

High-Speed Steel. In 1894 and 1895, Messrs. Taylor and White 
sought by experiment to produce a steel for cutting tools which 


328 


MACHINE SHOP WORK 


315 


would show a greater cutting efficiency in the shop. They finally 
developed the so-called Taylor and White high-speed steel, the 
forerunner of numerous brands of high speed steels. Cutting tools 



Fig. 368. Taylor Standard Cutting Contours 
Courtesy of Ready Tool Company, Bridgeport, Connecticut 


made from these steels have the peculiar quality of retaining their 
hardness at cutting temperatures much in excess of those sustained 
by tools made from carbon tool steel. For this reason cutting speeds 
have been materially increased. It is well to understand that the 
increased speed of cutting is not due to the new steels taking a greater 
hardness when heat treated, than the older steels, simply that 
they retain their hardness at temperatures which soften the cutting 
edges of carbon steel cutting tools to such 
an extent that their keenness is lost. 

Production Tools. In Machine Shop 
Work, Parts I-IV, the usual cutting tools 
have been treated. We will now discuss the 
more specialized forms used in production 
machine work. 

Turning Tools. Fig. 368 shows diagram- 
matically the Taylor form of cutting tools Fig. ^ tin ^ e ^ t ^g dard 
as used for rough and for finish turning. 

Fig. 369 shows these as modified by one manufacturer of lathe tool 
holders. Cutting tools shaped to these contours are much used in 
production turning. Fig. 370 shows how the tool approaches its cut. 



329 







































316 


MACHINE SHOP WORK 


As all cutting is a process of splitting it is very important 
that the cutting tool be properly set up as relates to its cut. 



Fig. 370. Rcd-E Roughing Tool 
Courtesy of Ready Tool Company, Bridgeport, Connecticut 


Fig. 327 illustrates the kind of surface these tools produce 
when correctly used. 

Planing Tools. The set of tools shown in Fig. 371 are cor¬ 
rectly ground for planer use. Due to the nature of their use, planer 
tools are necessarily of many contours. Their use is well illus¬ 
trated in Fig. 372. 

Milling Tools. The older type of milling cutter with its finer 
pitched teeth does not work well under production conditions 
of coarse feeding and heavy cuts. Coarse pitch cutters with maxi- 



Fig. 371. Set of Planer Tools Ground on Sellers’ Tool-Grinding Machine 
Courtesy of "Machinery”, New York City 


mum chip space between the teeth are now universally used in 
production milling. Fig. 346 shows a cutter which is constructed 
especially for coarse feeds and heavy cuts. 


330 











Fig. 372. Planer Tools of Different Form and Work to Which They Are Adapted 
Courtesy of “Machinery", New York City 




Fig. 373. Right and Wrong Method of Feeding Lubricant to Cutting Tool 
Courtesy of “Machinery", New York City 


331 





















































318 MACHINE SHOP WORK 

Drilling Tools. High-speed drills for production are shown 
in Figs. 348 and 349. In experimental tests on cast iron, drills 
made from high-speed steel are reported to have been fed to inch 
per revolution and at a cutting speed sufficiently high to give a 
hole depth of about 60 inches per minute. 

Cutting Lubrication. Lubrication of the cutting tool is com¬ 
mon when production cutting is being done upon wrought iron or 

steel. It has been found 
that at times an increased 
production of nearly 50 per 
cent can be obtained by 
forcing a heavy stream of 
cutting lubricant upon the 
cutting tool at the point 
where the metal is being sep¬ 
arated. The lubricant ap¬ 
pears to be most effective 
when it reaches the cutting 
edge at a slow velocity and 
in sufficient quantities to 
submerge the tool at the 
point of contact. Fig. 373 
shows diagrammatically 
right and wrong methods of 
application. 

In Fig. 338 the grind¬ 
ing wheel is nearly hidden 
by the flood of lubricant 
and Fig. 374 shows how gen¬ 
erously the cutting lubricant 
is flooded to a drill when 
cutting steel. 

Lubricants. The common cutting lubricants used in heavy 
machining operations are lard oil, mixtures of lard oil and paraffin 
oil, and the various mixtures of water, oil, soft soap, and sal soda, 
commonly termed “compounds”. Several mixtures of this sort 
are sold under specific trade names. 

Most of the modern manufacturing machine tools are provided 



Fig. 374. Drilling Operation Showing How 
Lubricant Floods the Work 
Courtesy of “ Machinery ”, New York City 


332 









MACHINE SHOP WORK 


319 


with a system for handling the cutting lubricant in large quantities. 
This usually consists of a supply tank with a settling chamber, an 
effective geared pump, and the distributing pipes. 

JIGS AND FIXTURES 

General Classification. The terms “jigs” and “fixtures” are 
rather loosely used by shopmen. While this is necessarily so in 
some cases, in most instances it is more correct to apply the term 
jig to a device which holds the work and automatically locates 
the cutting tool so that each piece produced is a duplicate of all 
the others. Fixtures, on the other hand, do not automatically 
locate the cutting tool. While fixtures may be used to produce 
duplicates, this result is usually gained by means of a cutting tool 
locating jig separated from the fixture itself. Fixtures are essen¬ 
tially work-holding devices. 

Object of These Tools. While several effects are gained by 
using jigs and fixtures, they all reduce to one thing, namely, pro¬ 
duction. For example, by the proper use of jigs and fixtures, pro¬ 
duction is made more uniform, giving interchangeability of parts. 
If jigs and fixtures are properly used, production is attended by a 
reduction of labor cost, both when the machine parts are being 
produced, and when the parts are assembled to produce the com¬ 
pleted machine. 

Importance. That jigs and fixtures are an important factor 
in modern production is clearly shown by a study of the various 
production cuts in this book. These illustrations for the most 
part show the machine in a working condition, and in nearly every 
case some special fixture or jig is holding the work or is guiding 
the tool. In some cases, the special work-holding device is a simple 
work chuck or a magnetic work chuck, in others the special devices 
are rather elaborate. 


Jig Design and Construction 

Many of the rules governing jig design hold true for fixtures, 
and jig design will be taken up first. 

Fundamental Principles of Design. Use of Jig. In jig design 
it is usual to first consider the uses to which it is to be put. If, for 
example, the piece for which the jig is made is to finally bear a 


333 


320 


MACHINE SHOP WORK 


fixed relation to some other machine part, it becomes necessary to 
consider not only the part being jigged, but also its relation to the 
other parts with which it is to be assembled. Again, if the piece 
being jigged is of special accuracy, the jig design may be different 
from that of a machine part in which no special accuracy is re¬ 
quired. In one case, the jig is both a rapid production tool and an 
interchangeability tool. In the other case, the jig is merely a con¬ 
venient tool for getting rapid production. 

As a Work Holder . It is usual in the design of jigs to next 
consider how the piece shall be held in the prospective jig. The 
points or surfaces upon the piece which are those best suited for 
location points and surfaces are decided upon. If the piece has been 
previously machined, the surface machined usually offers the best 
location to work from. If, on the other hand, the surfaces of the 
stock are rough, as in an ordinary casting, the selection of the locat¬ 
ing surfaces or surface is usually a more difficult one. Usually 
some surface or hole will be essentially more important than all 
the remaining surfaces or holes. In such a case, the jig designer 
uses location points which will position the important hole or sur¬ 
face, afterward considering the points of lesser importance. This 
he terms “working to or working from the important point”. A 
flat surface, if it has previously been machined, is usually located 
against a flat surface; if not previously machined, a flat surface 
should be given line or point contact. It is customary to locate 
a curved surface against a V or against points. 

Clamping. This refers to the particular devices which hold 
the piece being jigged against the location points or surfaces. The 
design should be such that the least number of clamping devices 
may be used, so that no unnecessary time is consumed in charging 
the jig, as this limits production unless the jigs are charged as a 
separate job. 

All clamping devices should exert their pressure, wherever 
possible, directly in line with the supporting points. If this is done 
the piece clamped will not be sprung out of shape. As an aid 
in understanding the already mentioned points, a simple jig will 
be illustrated and its construction described. 

Drill Jigs. While a study of the illustrations in this book 
will show the student that jigs are an important factor in all pro- 


334 


MACHINE SHOP WORK 


321 


duction machines, perhaps in no other machine is their importance 
so complete as in the drilling of holes. For this reason a drill jig 
will be used to illustrate jig construction. In the line drawing, 
Figs. 375 and 376, are 
shown the top and bottom 
views of a simple jig of the 
open box type designed to 
rapidly produce duplicate 
work. In Fig. 377 are 
shown two views'of a jig 
of the closed box type for 
rapid production of dupli¬ 
cate parts. While neither 
of these jigs are elaborate 
in either design or construction, they fairly represent their types. 

Types of Drill Jigs . Drill jigs are of three forms (a) plate 
jigs; (b) open box; (c) closed box. The plate jig usually consists 



Fig. 375. Typical Open Box Drill Jig 
Courtesy of “American Machinist ” 



Fig. 376. Bottom View of Box Drill Jig Shown in Fig. 375 
Courtesy of “ American Machinist ” 


of a flat plate with located bushings which is positioned on the work 
and clamped to it. The open box type, as shown in Figs. 375 and 
376, consists of a casting provided with legs or feet. The piece 
jigged is clamped to the lower or under surface of the jig body. 


335 











322 


MACHINE SHOP WORK 


The closed box type is such that the piece to be jigged is positioned 
in a box which may be entirely or partially closed. In the lower 

view, Fig. 377, the box, 
as shown, is open on one 
side and partially so on 
another side. 

Locating Work in 
Drill Jig's. Fig. 378 shows 
the use of pins or studs 
used as side-locating points 
in simple jig work, and 
Fig. 379 shows how V’s 
are similarly used on 




Fig. 377. Two Views of Closed Box Drill Jig 
Courtesy of “American Machinist ” 


curved surfaces. While these are simple examples, they illustrate a 
principle which can easily be applied to more complicated cases. 


336 



























MACHINE SHOP WORK 


323 


The use of locating pads is shown in Fig. 380, and Fig. 381 
shows how an inserted pin may be used for supporting a plane 
surface. Where pins are used for location points, Fig. 378, the sides 
against which the pieces are 
located are usually flatted (V—sr - 
somewhat to bring surface ( O ) 
contact rather than line con- 
tact. Hardening the pins will Fig. 378. Method of Locating Stubs or Pins 

also prevent excessive wear. 

Locating Points with Adjustments. In some cases, it is well 
to have locating surfaces or points adjustable. In Fig. 381 the 
inserted pin, if threaded into base B could, for example, be raised 
to some other position from that shown. Some jig designers, 
instead of the V-block shown in Fig. 379, use two set screws hor¬ 
izontally set at an angle of 45 degrees with one another, bringing 
the curved surface against their points. 

, Clamping . This is done in a great variety of ways and many 
of the devices are very ingenious. However, they nearly all reduce 
to some form of clamp either straight, bent, or forked, pressed against 
the work by either a set screw, a cap screw, or a cam. In Fig. 375 
it will be noted that the clamping is done by a strap similar to that 
shown in Fig. 382, and the piece is pushed into position by knurled 
head set screws. In Fig. 377 set screws are used, supplemented 




by a hinged leaf carrying a bushing and pressing against the piece 
of work. Fig. 383 shows favorite forms of cam clamping devices. 

Jig Body. While steel may be used for the body or frame of 
a jig, it is a usual thing to use cast iron. If cast iron is used the jig 


337 
























324 


MACHINE SHOP WORK 


can be more or less completely worked out in the pattern, and 
possibilities of alteration in design may show as desirable. When 
it is realized that many shops use jigs weighing hundreds of pounds 




c= 




Fig. 382. Clamp Strap 


in their production work, it 
is clearly seen why cast iron 
is largely used for jig bodies. 

Bearing Points. Only in 
the smaller sizes do drill jigs 
rest upon a surface of any 
considerable area. It will be 
noted, by reference to Figs. 


375, 376, and 377, that supporting points, termed feet, are pro¬ 
vided on those sides of the jig which are to rest upon the work 
table. The height of the feet must be sufficient to clear all bushings 


338 
























































MACHINE SHOP WORK 


325 


holding screws on other projecting parts. Also their bearing area 
must be sufficiently large to prevent their slipping into the bolt 




Fig. 333. Diagrams Showing Cams or Eccentrics Used for Clamping 
Courtesy of “ Machinery ”, New York Citj 



Fig. 384. Typical Bushings: Upper Line—Guiding Lining Bushings for Drill Jigs; Lower 
Left—Screw Bushing for Locating Work Central with Hole; Lower Center—Screw 
Bushing for Locating Round Work by Recesses; Lower Right—Floating Bushing 
Courtesy of “ Machinery ”, New York City 


slots often found in work tables. Whenever possible the jig should 
be provided with four feet instead of three. 


339 
































































































326 


MACHINE SHOP WORK 


TABLE XIX 

Dimensions of Stationary Drill Bushings* 





q 


c 

5 C 




X— 1 — — " 


*- L -* 



A 

B 

L 

A 

B 

L 

A 

B 

L 

A 

B 

L 

A 

3 

16 

3 

8 

_9_ 

16 

13 

16 

H 

1A 

1A 

2 

1 -4- 

1 16 

1 il 

1 16 

2f 

1 

8 

1 

4 

1 

2 

5 

8 

7 

8 

H 

li 

il 

21 

li 

1 8 

2 

2 

A 

_5_ 

16 

1 

2 

11 

16 

11 

16 

if 

1A 

i A 

21 

ltt 

H 

21 

1 

4 

I 

5 

8 

4 

1 

h 

H 

1 4 

1 8 

21 

If 

21 

21 

16 

1 

2 

5 

13 

T6 

H 

h 

i A 

ltt 

21 

m 

2A 

2A 

8 

9 

16 

3 

7 

8 

i A 

H 

if 

If 

2* 

H 

2f 

2f 

A 

5 

8 

1 

8 

15 

16 

li 

i! 

1A 

HI 

21 

1 15 

ll6 

2A 

2A 

1 

2 

11 

16 

1 

1 

if 

21 

11 

H 

21 

2 

2f 

21 


TABLE XX 

Dimensions of Lining Bushings* 



A 

B 

L 

A 

B 

L 

A 

B 

L 

5 

I J 

1 

2 

1 

2 

H 

H 

11 

21 

21 

21 

3 

8 

A 

1 

2 

11 

11 

11 

2A 

2tt 

2f 

A 

5 

8 

5 

8 

i A 

ltt 

If 

21 

2f 

21 

A 

1 3 

16 

5 

8 

if 

If 

n 

2A 

21 

21 

5 

7 

8 

3 

4 

1A 

1 13 

-ire 

2 

21 

3 

3 

11 

16 

15 

16 

7 

8 

1A 

1 15 

1 16 

21 

2A 

3A 

31 

3 

4 

1 

1 

1 8 

2 

21 

21 

31 

31 

13 
] 0 

11 

11 

If 

21 

21 

2H 

3A 

31 

15. 

16 

H 

n 

m. 

2A 

21 

2f 

31 

31 

1 

U 

if 

ii 

2| 

2f 

. . . 

. . . 

.. 

l-v 

1A 

ii 

itt 

2A 

21 





♦Courtesy of “Machinery”, New York City. 


340 






































































MACHINE SHOP WORK 327 


TABLE XXI 

Dimensions of Removable Drill Bushings* 


A 

B 

c 

D 

E 

F 

H 

i 

K 

£ 

A 

1 

2 

8 

5 

8 

| 

f 

1 

2 

A 

Jj6 

3 

1 

f 

5 

8 

5 

8 

f 

f 

A 

1 

4 

A 

5 

8 

1 

8 

1 

4 

3 

£ 

5 

8 

A 

A 

A 

5 

f 

f 

1 

' 1 

8 

f 

3 

A 

I 

1 

8 

4 

I 

8 

7 

8 

7 

8 

1 

8 

2 

A 

* 

ff 

7 

8 

I 

8 

1 

1 

f 

7 

8 

A 

f 

f 

1 

f 

H 

1 

f 

1 

8 

A 

A 

if 

If 

1 

8 

H 

If 

f 

1 

A 

f 

it 

H 

A 

1A 

H 

f 

If 

A 


1 

If 

A 

l A 

H 

f 

If 

A 

f 

l A 

H 

A 

iff 

If 

f 

H 

A 

tt 

if 

If 

A 

iff 

If 

f 

H 

A 

f 

if 

If 

A 

ift 

If 

f 

If 

A 

ft 

l A 

If 

A 

HI 

If 

f 

If 

A 

l 

if 

If 

i 

4 

2f 

If 

A 

If 

A 

l A 

l A 

2 

I 

4 

2f 

If 

A 

If 

A 

1£ 

1A 

21 

1 

4 

2f 

2 

A 

1 16 

A 

1A 

if 

2f 

I 

4 

2f 

2 

A 

1ft 

A 

ir 

if 

21 

A 

2A 

2f 

A 

1ft 

f 

1A 

iff 

2f 

A 

2A 

2f 

A 

2A 

■ f 

if 

if 

2f 

A 

2 ff 

2f 

A 

2A 

f 

1A 

lit 

2f 

A 

2ft 

2f 

A 

2A 

i 

8 

if 

2£ 

2f 

f 

3 

21 

A 

2A 

8 

1A 

2A 

21 

f 

3f 

2f 

A 

2A 

1 

8 

if 

2f 

2f 

f 

3f 

2f 

A 

2A 

f 

iff 

2A 

2f 

f 

31 

2f 

A 

2A 

f 

if 

2f 

3 

f 

3f 

2f 

A 

2A 

£ 

ill 

2A 

31 

f 

3f 

3 

i 


A 

if 

2f 

31 

f 

3f 

3f 

i 

2ft 

A 

i * 5 

1t6 

2ff 

3f 

f 

3f 

3f 

i 

2ft 

A 

2 

2f 

3f 

f 

4 

3f 

* 

3A 

A 



: t— 

..fi 

ll 


t ... 

1] 


.L 

— 
—|/r 

27—f 

sk 

■- c -—— 



Guide Bushing. The soft body of the jig cannot be used to 
guide the drill if much service is required of the jig. In all pro¬ 
duction work, the guide holes for the drills are lined with hardened 


♦Courtesy of “Machinery”, New York City. 









































328 


MACHINE SHOP WORK 


TABLE XXII 

Bushings for Holes Reamed with Rose Chucking Reamers* 


to 

rr ^- 

Tl [f 



=n r 

f 


- V 

J l 1 


V 

y 

01 

t) 

1 

—H- 

►O 

-- F -" 

—K -- 

I..- 1 — 1 

♦ ^ 

-o 

1-- F -- 

_— /-- 


-- F —- 


A 

B 

c 

D 

E 

F 

G 

H 

I 

K 

M 

N 

0 

3 

4 

11 

16 

H 

If 

H 

H 

A 

i 

4 

1A 

If 

I 

8 

H 

A 

1 3 

I 6 

3 

4 

i A 

Iff 

If 

1A 

A 

1 

4 

if 

1A 

1 

8 

If 

A 

7 

8 

1_3 

16 

if 

If 

If 

if 

A 

f 

1A 

if 

i 

If 

A 

15 

16 

7 

8 

1A 

Iff 

If 

1A 

_3_ 

1 6 

f 

if 

iff 

f 

H 

A 

1 

1 5 

16 

if 

H 

If 

if 

1 

4 

A 

if 

iff 

A 

If 

i 

8 

1* 

1 

1A 

1 15 

lie 

H 

1 5. 

1 8 

1 

4 

A 

if 

iff 

A 

If 

1 

8 

H 

1A 

1 8 

2 

If 

Iff 

1 

4 

A 

iff 

2 

A 

If 

1 

8 

1* 

H 

1 16 

2f 

2 

If 

1 

4 

A 

2 

2A 

A 

If 

1 

8 

H 

i A 

1 13 

2A 

2f 

H 

A 

f 

2A 

21 

A 

2 

1 

1A 

U 

1 15 

1 16 

2A 

21 

2 

A 

1 

8 

2A 

2f 

A 

21 

1 

H 

1A 

2 

2f 

2f 

2f 

A 

8 

2A 

2f 

A 

21 

1 

l A 

if 

2A 

2A 

3f 

2f 

A 

f 

2A 

21 

A 

21 

1 

if 

1 A 

2f 

2f 

2f 

21 ' 

A 

8 

2ff 

21 

A 

21 

1 

1A 


2A 

2ff 

2f 

2f 

8 

A 

Q1 

L 8 

2ff 

A 

21 

1 

H 

1A 

2» 

3 

2f 

2f 

1 

8 

A 

3 

3A 

A 

2f 

f 

iff 

if 

2A 

3A 

2f 

2f 

3 

8 

A 

3f 

3A 

A 

21 

1 

if 

iff 

2f 

3f 

2f 

2f 

3 

8 

A 

31 

3A 

A 

2f 

1 

8 

iff 

if 

2A 

3A 

3 

3 

A 

f 

3A 

3f 

i 

4 

2 If 

A 

if 

iff 

2f 

3f 

3 

3f 

A 

f 

3A 

31 

1 

4 

2ff 

A 

HI 

if 

2ff 

3A 

3f 

3f 

A 

f 

3ff 

3f 

1 

4 

2 If 

A 

2 

iff 

2! 

3f 

3f 

31 

A 

1 

2 

3ff 

3f 

1 

4 

2ff 

A 

2A 

2 

0 15 

3A 

3f 

3f 

1 

2 

5 

8 

4 

41 

1 

4 

31 

A 

21 

2A 

3 

3f 

3f 

3f 

i 

5 

8 

4 

41 

1 

4 

31 

A 

2A 

2f 

3A 

3ff 

3f 

3f 

1 

2 

5 

8 

41 

41 

1 

4 

31 

A 

21 

2A 

3* 

3f 

31 

3f 

1 

2 

5 

8 

41 

41 

1 

4 

31 

A 

2| 

2A 

3f 

4f 

3f 

3f 

1 

2 

1 

8 

41 

4f 

1 

4 

3f 

A 

2* 

2 A 

3f 

4f 

4 

4 

1 

2 

5 

8 

4f 

4f 

1 

4 

3f 

A 

2f 

2A 

3f 

4* 

4f 

41 

1 

2 

5 

8 

41 

4f 

1 

4 

3f 

A 

2f 

2ff 

3f 

4f 

4i 

41 

1 

2 

5 

8 

4f 

4f 

I 

4 

4 

A 


tool steel bushings, ground true inside and out to accurate dimen¬ 
sions. Fig. 384 illustrates different forms of guide bushings and 
Tables XIX, XX, XXI, and XXII give accepted dimensions. The 
several types of bushings are known, from their use or by their 
construction, as tight bushings, lining bushings, slip bushings, screw 
bushings, etc. 

♦Courtesy of “Machinery”, New York City. 


342 
















































MACHINE SHOP WORK 


329 


Tolerances. A jig is usually a duplicating tool as well as a 
production tool. In all machine work certain standards of accuracy 
prevail. Exact dimensions are hard to obtain in any "work, and 
certain commercial variations from the exact dimensions are 
allowable. Such variations from exactness of dimensions are known 
as tolerances. For example, an allowable tolerance of 0.0005 inch 
plus or minus (±) might be used in grinding a certain piece of 
work, and all pieces ground would, if within these limits, be 
considered commercially exact. 

In jig construction certain tolerances are agreed upon by the 
user of the tool, as commercially possible. The following tolerances 
are from the practice of the Taft-Pierce Company, and are those 
used for tool and jig design: 

Information and Limits to Be Placed on Drawings 

The following are two important essentials that must be carefully executed 
on all drawings before the drawings are submitted to the checker for his signature, 
and are to be considered as aids for the better conception and reasoning of the 
workman, in whose hands the work is placed when “doping out” the intent 
and purpose of the drawings. 

Next to the accuracy, the efficiency and clearness with which these aids 
are accomplished are of the greatest importance: 

(1) State accurately the amount of limits of tolerance that may be per¬ 
mitted on all dimensions. (See sheet describing methods of expressing limits.) 

(2) Issue with each drawing specifications written on information blanks 
provided for the purpose, describing the requirements of the drawing and giving 
any information that will be of value to the workmen. 

Limits of Tolerance as Adopted by the Taft=Pierce Company 

Statement: If a limit can be permitted above and below the dimension, 
specify the limit thus: (d=) giving the amount of limit tolerated. If a limit 
can only be permitted below the dimension, specify it thus: (—) giving the 
amount of limit tolerated. If a limit can only be permitted above the dimension 
specify it thus: (+) giving the amount of limit tolerated. 

Fractions. Unless limits are specified, vulgar fractions are capable in the 
main of a wide variation of limitation. For the purpose of fixing a standard, 
however, it shall always be understood that in the event that a fraction is not 
accompanied by a limit, a minimum limit of (d=) .010 is permissible. Fractions 
that must he held closer than this must he accompanied hy a specified amount of limit. 

Amounts: 2-Place Decimals. If tolerance is not added, a limit of (±) 
.005 is permissible. 

3-Place and 4-Place Decimals. A 3- or 4-place decimal should be used 
only when absolutely necessary. If tolerance is not added, a limit of (i) .0015 
is permissible. 


343 


330 


MACHINE SHOP WORK 


3-Place and 4-Place Decimals. Whenever through necessity three or four 
places must be accurately obtained, the dimension shall be marked EXACT. 

Guide Bushings. Locating the Guide Bushings. While there 
are a great variety of methods used when locating the centers of the 

holes, if exactness is desired, 
the located centers are usually 
positioned by making use of 
the jig buttons shown in 
Fig. 385. These are hardened 
and ground tool steel cylin¬ 
ders with the ends ground 

Fig. 385. Tool-Maker’s Buttons with Screws and T n 110 „ 

Washers for jig Work parallel. .in use tne center 

distances, called for on the 
drawing of the jigged piece, are located approximately in position 
on the face of the jig. Each button as purchased is furnished 
with a clamping screw whose body fits loosely in the axial hole 
in the button. Figs. 386 and 387 show how the buttons may be 




Fig. 386. Positioning Buttons with Micrometer Caliper 

accurately positioned using precision tools. It will be noted that 
in each case shown the buttons are first positioned by lightly 
clamping them to an approximately accurate layout, and after¬ 
ward bringing them to accurate position by measurements made 
with precision tools. 
























































MACHINE SHOP WORK 


331 



Boring Hole for Guide Bushings. Fig. 388 shows the hole being 
bored. Previous to the boring, the plate is clamped to a lathe face¬ 
plate and shifted to a posi¬ 
tion where the accurately 
positioned button will indi¬ 
cate true with the feeler of 
a good indicator placed 
against its surface. When 
the button rotates true, it 
is removed, the hole is 
roughly drilled, afterward 
accurately bored, as shown 
in the cut, and the hard¬ 
ened and ground tool steel 
bushings pressed into place. 

Operating the Jig. If 
the jig is of a proper design 
and construction, the oper¬ 
ator should have little 
trouble in its use. All 
locating points and surfaces 
should be plainly visible. 


Fig. 387. Positioning Buttons with Vernier Caliper 



Fig. 388. Boring Hole for Guide Bushing 


345 








332 


MACHINE SHOP WORK 


the work should go into the jig only when properly positioned and 
the clamping done with despatch, the various tools should spindle 
as shown in Fig. 349, and the operator should handily use each 
spindle in logical order. The jig is then discharged and newly 
recharged. 

Spotting. Hand scraped or other plane surfaces are given an 
attractive appearance by what is termed “spotting”. A skilful 



Fig. 389. Typical “Spotting” Pattern on Surface Plate 


worker with the hand scraper will cover a plane surface with 
regular spots in an artistic manner. Fig. 389 shows sections so 
treated. If the spots are small rectangles, the result is termed 
“snow flaking”. Another method of handling the scraper results in 
small crescents or “half moons”, this result is known as “frosting”. 
In all cases where work is spotted, it results in a pleasing effect, 
and adds to the “classiness” of the machine or jig. The scraping 
pattern has also the effect of making the workman more careful 
of such surfaces. 


346 









MACHINE SHOP WORK 


333 


Fixtures 

Importance. When work-holding devices are used in machine 
practice they are ordinarily termed fixtures. That these are 
important adjuncts of the modern machine tool is made evident 



Fig. 390. Typical Milling Fixture 


by a study of the various 
production illustrations 
in this book. For exam¬ 
ple, take the milling jobs 
shown, and it at once 
becomes apparent that 
the fixtures are a prin¬ 
cipal item in the produc¬ 
tion figures given, and so 
on through the whole list 
of production machines. 

Milling Fixtures. 

While in some cases fix¬ 
tures can be used inter¬ 
changeably upon planers, 
shapers, boring mills, and 

milling machines, it is Fig. 391. Typical Boring Fixture 



347 






334 


MACHINE SHOP WORK 


more usual to find them designed for the particular machine on 
which they are to be used. In Fig. 390 is shown a milling 
machine fixture of a simple form and construction designed 
to hold the base of a small bench grinder, while the upper surfaces 
of the bearing boxes are being machined. This is done with the 
gang of cutters shown in the illustration. Such fixtures as this 
cost little and can be used by inexperienced employes. The increased 



Fig. 392. Typical Planer Fixture, Showing Set-Up for Planing Twenty Square 
Tables at One Setting 

Courtesy of Worcester Polytechnic Institute Shops, Worcester, Massachusetts 


production alone, made possible by even so simple a fixture as the 
one shown, warrants its construction. 

Boring Fixtures. Fig. 391 shows a fixture used in boring out 
the head casting of a ball-bearing lathe. In this fixture, the casting 
is held while being bored. As the spindle holes are located by the 
bushed holes for the boring bar, it is perhaps more of a “jig” than 
a “fixture”. However, its use is evident from the cut. 

Planer Fixtures. Planer fixtures are usually simpler in design 
and construction than those in use on either the boring or the milling 


348 




MACHINE SHOP WORK 335 

machine. Fig. 392 is illustrative of the simplicity of planer fixtures. 
The cut shows it as made for holding a string of square tables such 
as are used on sensitive drillers. As shown in the illustration, a 
double string of tables are mounted and both of the tool heads 
are used. 

BALL BEARINGS 

Uses of Ball Bearings. The claims made for the use of ball 
bearings in preference to plain bearings are several in number as 



Pig. 393. Auburn Self-Contained Ball Thrust Bearing 
Courtesy of Auburn Ball Bearing Company, Rochester, New York 


follows: Less wear, less frictional resistance, more compact, non¬ 
heating in use, less fitting than plain bearings, better shaft alignment. 

Until recently very little reliable information could be obtained 
relative to ball bearings and today it is probable that their use on 
machine tools is much less 
than it should be. Their 
extended use on motor cars 
and bicycles has shown defi¬ 
nitely just what their value 
is in such lines, but machine 
tool builders have probably 
been ultra-conservative in 
their use. In the high-speed 
drilling machines, their use 
has been remarkably suc¬ 
cessful. Any of the reliable manufacturers of such bearings will 
furnish performance figures showing the possibilities of their use. 



Fig. 394. 


Hess-Bright Thrust Bearing with a Lining 
Washer and Enclosing Case 


349 
































































336 


MACHINE SHOP WORK 


Types of Bearings. Ball bearings are known generally under 
two headings: ‘‘Radial” and “Thrust”. In the radial bearing, 
the load pressure is at right angles or normal to the shaft axis, while 
in the thrust bearing the load pressure is parallel 
to the axis, or, in other words, the pressure is axial. 

Fig. 393 is representative of the usual thrust 
bearing, while Fig. 394 illustrates diagrammatically 
the Hess-Bright thrust bearing with ball separating 
retainers. 

Figs. 395 and 396 are representative of the best 
type of radial ball bearings. Radial ball bearings 
are made in what is known as the single type and 
the double type. In other words, bearings may 
be obtained with either a single row or race of balls, 
or they may be obtained with two rows of balls. 
While radial bearings are not generally supposed 
to take an axial load or thrust, many of the better 
radial types will allow a certain amount of axial 
thrust under favorable conditions. 

Load Capacities. Tables XXIII and XXIV 
give load carrying capacities of radial and of axial 
ball bearings used under light, medium, and heavy 
loading. 

Lubrication. While it was at one time thought 
Radial BaifBearing that ball bearings needed no lubrication, this was 




Fig. 396. S. K. F. Radial Bearing Showing Parts and Assembled Bearing Complete 


350 







MACHINE SHOP WORK 


337 


TABLE XXIII 

Load Capacities of Radial Ball Bearings* 


Diameter 

Bore 

Outside 

Diameter 

W IDTH 

Revolutions 

per Minute 

Milli¬ 

meters 

Inches 

Milli¬ 

meters 

Inches 

Milli¬ 

meters 

Inches 

300 

600 

1200 

2400 

Maximum L 

oad, Pounds 

EXTRA HEAVY TYP 

•E 

17 


0.6693 

62 

2.4409 

20 

0.7874 

1,100 

880 

680 

540 

20 


0.7874 

72 

2.8346 

23 

0.9055 

1,450 

1,150 

860 

710 

25 


0.9843 

80 

3.1496 

25 

0.9843 

2,000 

1,600 

1,200 

980 

30 


1.1811 

90 

3.5433 

28 

1.1024 

2,400 

1,925 

1,450 

1,175 

35 


1.3780 

100 

3.9370 

30 

1.1811 

2,850 

2,290 

1,700 

1,400 

40 


1.5748 

110 

4.3307 

33 

1.2992 

3,300 

2,650 

2,000 

1,650 

45 


1.7717 

120 

4.7244 

35 

1.3780 

3,850 

3,075 

2,400 

1,890 

50 


1.9685 

130 

5.1181 

37 

1.4567 

4,400 

3,500 

2,650 

2,150 

55 


2.1654 

140 

5.5118 

40 

1.5748 

5,100 

4,075 

3,100 

2,500 

60 


2.3622 

150 

5.9055 

42 

1.6536 

5,700 

4,560 

3,500 

2,800 

65 


2.5591 

160 

6.2992 

45 

1.7717 

6,800 

5,450 

4,200 

3,350 

70 


2.7559 

180 

7.0866 

50 

1.9685 

8,000 

6,400 

4,850 

3,925 

75 


2.9528 

190 

7.4803 

53 

2.0867 

9,200 

7,350 

5,500 

4,500 

80 


3.1496 

200 

7.8740 

57 

2.2441 

10,600 

8,500 

6,400 

5,200 

85 


3.3465 

210 

8.2677 

60 

2.3622 

12,000 

9,600 

7,300 

5,900 

90 


3.5433 

225 

8.8583 

63 

2.4803 

13,600 

10,900 

8,200 

6,650 

95 


3.7402 

250 

9.8425 

67 

2.6378 

15,400 

12,250 

9,200 

7,550 

100 


3.9370 

265 

10.4331 

70 

2.7559 

17,400 

13,900 

10,400 

8,553 

HEAVY TYPE 

17 


0.669 

62 

2.441 

17 

0.669 

750 

600 

450 

370 

20 


0.787 

72 

2.835 

19 

0.748 

1,000 

800 

600 

490 

25 


0.981 

80 

3.150 

21 

0.827 

1,200 

960 

750 

590 

30 


1.181 

90 

3.543 

23 

0.905 

1,650 

1,325 

920 

810 

35 


1.378 

100 

3.937 

25 

0.984 

1,850 

1,475 

1,100 

910 

40 


1.575 

110 

4.331 

27 

1.063 

2,200 

1,750 

1,300 

1,075 

45 


1.772 

120 

4.724 

29 

1.142 

3,000 

2,400 

1,750 

1,475 

50 


1.968 

130 

5.118 

31 

1.220 

3,400 

2,725 

2,100 

1,675 

55 


2.165 

140 

5.512 

33 

1.299 

4,000 

3,200 

2,400 

1,950 

60 


2.362 

150 

5.905 

35 

1.378 

4,400 

3,525 

2,650 

2,150 

65 


2.559 

160 

6.299 

37 

1.457 

5,100 

4,100 

3,100 

2,500 

70 


2.756 

180 

7.087 

42 

1.654 

5,700 

4,550 

3,500 

2,800 

75 


2.953 

190 

7.480 

45 

1.772 

7,000 

5,600 

4,200 

3,400 

80 


3.150 

200 

7.874 

48 

1.S90 

8,600 

6,875 

5,100 

4,200 

85 


3.346 

210 

8.268 

52 

2.047 

9.200 

7,350 

5,500 

4,500 

90 


3.543 

225 

8.858 

54 

2.126 

10,000 

8,000 

6,200 

4,900 

95 


3.740 

250 

9.842 

55 

2.165 

12,000 

9,600 

7,000 

5,900 

100 


3.937 

265 

10.433 

60 

2.362 

13,900 

11,100 

8,400 

6,800 


* S. K. F Ball Bearing Company. 


an absurd attitude and ball bearings are now greased in some way. 
Whatever the oil or grease used, it must be such as will prevent rust 
and be free from any acid or alkali likely to attack the surfaces of 
the balls or the ball races. A good oil or grease is one that keeps 
the surfaces bright and brilliant after months of use, and besides 
furnishes the desired lubrication. Vaseline, vaseline oil, or mineral 


351 







































33S 


MACHINE SHOP WORK 


TABLE XXIII—(Continued) 


Load Capacities of Radial Ball Bearings 


Diameter 

Bore 

Outside 

Diameter 

Width 

Revolutions 

per Minute 

Milli¬ 

meters 

Inches 

Milli¬ 

meters 

Inches 

Milli¬ 
meter s 

Inches 

300 

600 

1200 

2400 

Maximum Load, Pound.! 




MEDIUM 

TYPE 





10 

0.393 

35 

1.378 

11 

0.433 

290 

230 

175 

140 

12 

0.172 

37 

1.456 

12 

0.472 

330 

265 

200 

165 

15 

0.590 

42 

1.653 

13 

0.511 

375 

300 

220 

185 

17 

0.669 

47 

1.850 

14 

0.551 

490 

390 

290 

240 

20 

0.787 

52 

2.047 

15 

0.590 

600 

480 

360 

295 

25 

0.984 

62 

2.440 

17 

0.669 

880 

705 

530 

430 

30 

1.181 

72 

2.834 

19 

0.748 

1,100 

880 

660 

540 

35 

1.378 

80 

3.149 

21 

0.826 

1,400 

1,125 

840 

685 

40 

1.574 

90 

3.543 

23 

0.905 

1,650 

1,325 

990 

800 

45 

1.771 

100 

3.937 

25 

0.984 

2,200 

1,760 

1,300 

1,100 

50 

1.968 

110 

4.330 

27 

1.063 

2,750 

2,200 

1,650 

1,350 

55 

2.165 

120 

4.724 

29 

1.141 

3,300 

2,650 

2,000 

1,600 

60 

2.362 

130 

5.118 

31 

1.220 

3,850 

3,100 

2,300 

1,850 

65 

2.559 

140 

5.511 

33 

1.299 

4,200 

3,350 

2,550 

2,050 

70 

2.755 

150 

5.905 

35 

1.378 

4,500 

3,600 

2,750 

2,200 

75 

2.952 

160 

6.299 

37 

1.456 

5,300 

4,250 

3,100 

2,600 

80 

3.149 

170 

6.692 

39 

1.535 

6,000 

4,800 

3,500 

2,950 

85 

3.346 

ISO 

7.086 

41 

1.614 

7,500 

6,000 

4,400 

3,700 

90 

3.543 

190 

7.480 

43 

1.692 

8,400 

6,700 

5,100 

4,125 

100 

3.937 

215 

8.464 

47 

1.850 

10,400 

8,325 

6,200 

5,100 

110 

4.330 

240 

9.448 

50 

1.968 

13,200 

10,500 

7,900 

6,500 

LIGHT TYPE 

10 

0.393 

30 

1.181 

9 

0.354 

220 

175 

120 

108 

12 

0.472 

32 

1.259 

10 

0.393 

240 

195 

140 

115 

15 

0.590 

35 

1.378 

11 

0.433 

290 

230 

175 

140 

17 

0.669 

40 

1.574 

12 

0.472 

350 

280 

210 

170 

20 

0.787 

47 

1.850 

14 

0.551 

440 

350 

260 

215 

25 

0.984 

52 

2.047 

15 

0.590 

530 

425 

310 

260 

30 

1.181 

62 

2.440 

16 

0.629 

820 

655 

480 

400 

35 

1.378 

72 

2.834 

17 

0.669 

880 

780 

530 

430 

40 

1.574 

80 

3.149 

18 

0.708 

1,200 

960 

700 

590 

45 

1.771 

85 

3.346 

19 

0.74S 

1,450 

1,150 

860 

710 

50 

1.968 

90 

3.543 

20 

0.787 

1,650 

1,350 

970 

810 

55 

2.165 

100 

3.937 

21 

0.826 

1,800 

1,450 

1,100 

880 

60 

2.362 

110 

4.330 

22 

0.866 

2,200 

1,750 

1,300 

1,080 

65 

2.559 

120 

4.724 

23 

0.905 

2,550 

2,050 

1,550 

1,250 

70 

2.755 

125 

4.921 

24 

0.944 

2,750 

2,200 

1,650 

1,350 

75 

2.952 

130 

5.118 

25 

0.984 

3,100 

2,480 

1,850 

1,520 

80 

3.149 

140 

5.511 

26 

1.023 

3,750 

3,000 

2,200 

1,835 

85 

3.346 

150 

5.905 

28 

1.102 

4,000 

3,200 

2,400 

1,960 

90 

3.543 

160 

6.299 

30 

1.181 

4,400 

3,520 

2,650 

2,150 

100 

3.937 

180 

7.086 

34 

1.338 

5,700 

4,560 

3,500 

2,830 

110 

4.330 

200 

7.874' 

38 

1.496 

7,500 

6,000 

4,400 

3,650 


oil, are each good for the purpose. Usually these are combined 
in quantities to give the desired consistency for the speed at which 
the bearing is rotated. 


352 







































MACHINE SHOP WORK 


339 


TABLE XXIV 

Loads for Thrust Collar Bearings* 


No. 

OP 

Balls 

Size 

OF 

Balls 

Revolutions per Minute 

1500 

1000 

500 

300 

150 

100 

50 

25 

10 



MEDIUM WEIGHT, LOAD IN POUNDS 

8 



145 

190 

245 

285 

333 

395 

540 

66< 

3 

1,100 

10 

i 

185 

245 

310 

365 

430 

505 

660 

825 

1,320 

13 

i 

240 

320 

395 

485 

550 

650 

870 

1,080 

1,760 

16 


: 

295 

395 

495 

585 

680 

770 

1,045 

1,355 

2,200 

18 


: 

330 

440 

550 

660 

770 

880 

1,175 

1,520 

2,420 

17 


V 

440 

550 

660 

880 

990 

1,285 

1,725 

2,245 

3,300 

18 


V 

550 

660 

770 

990 

1,210 

1,395 

1,905 

2,400 

3,520 

17 


: 

660 

770 

880 

1,210 

1,540 

1,890 

2,585 

3,255 

4,620 

19 


• 

770 

880 

1,100 

1,430 

1,760 

2,110 

2,880 

3,650 

5,060 

18 


V 

880 

1,100 

1,320 

1,650 

2,200 

2,465 

3,255 

4,355 

6,380 

19 


rs 

990 

1,210 

1,540 

1,870 

2,420 

2,605 

3,430 

4,620 

6,820 

18 



1,210 

1,430 

1,760 

2,200 

2,640 

3,235 

4,235 

5,720 

8,360 

19 

j 


1,320 

1,540 

1,980 

2,420 

3,080 

3,300 

4,335 

6,070 

8,800 

20 

* 

1,430 

1,650 

2,090 

2,530 

3,300 

3,485 

4,555 

6,380 

9,240 

19 


ft 

1,540 

1,760 

2,420 

2,640 

3,740 

4,180 

5,455 

8,790 

11,000 

19 

i 


1,870 

2,090 

2,860 

3,300 

4,400 

4,950 

6,600 

9,295 

13,200 

20 



1,980 

2,200 

2,970 

3,520 

4,620 

5,225 

6,950 

9,790 

13,860 

19 


i 

2,200 

2,530 

3,520 

4,180 

5,280 

5,995 

7,965 

11,255 

15,400 

20 


1 

2,420 

2,640 

3,740 

4,400 

5,500 

6,510 

8,745 

11,440 

16,280 

19 



2,640 

3,080 

3,960 

4,840 

5,940 

7,370 

9,845 

12,640 

17,600 

19 


i 

2,860 

3,520 

4,840 

5,500 

7,040 

8,635 

11,605 

14,830 

22,000 

19 

\ 


3,080 

4,180 

5,280 

6,380 

8,140 

10,340 

13,970 

17,600 

24,200 

19 

1 


3,740 

4,840 

6,600 

8,140 

10,560 

13,510 

18,215 

23,010 

28,600 

LIGHT WEIGHT, LOAD IN POUNDS 

21 


ft 

640 

770 

900 

1,155 

1,410 

1,630 

2,200 

2,970 

4,180 

23 


ft 

705 

860 

990 

1,265 

1,540 

1,760 

2,420 

3,255 

4,620 

21 


P 

860 

990 

1,210 

1,595 

1,980 

2,245 

3,035 

4,005 

5,500 

22 


f 

905 

1,045 

1,265 

1,675 

2,090 

2,355 

3,170 

4,180 

5,940 

21 



1,100 

1,320 

1,705 

2,090 

2,530 

2,970 

4,025 

5,280 

7,480 

22 



1,155 

1,385 

1,785 

2,200 

2,775 

3,125 

4,225 

5,500 

7,920 

23 



1,210 

1,455 

1,870 

2,310 

2,860 

3,255 

4,400 

5,785 

8,140 

25 



1,320 

1,585 

2,035 

2,530 

3,080 

3,520 

4,775 

6,270 

9,020 

27 


vV; 

1,430 

1,715 

2,200 

2,750 

3,300 

3,830 

5,170 

6,765 

9,680 

28 


% 

1,485 

1,785 

2,310 

2,860 

3,410 

3,960 

5,370 

7,040 

10,120 

29 


* 

1,540 

1,850 

2,420 

2,970 

3,520 

4,115 

5,545 

7,260 

10,340 

30 


S 

1,595 

1,915 

2,530 

3,080 

3,630 

4,270 

5,720 

7,525 

10,780 


* The Hess-Bright Manufacturing Company. 

MAGNETIC CHUCKS 

Uses in Production Work. A magnetic chuck is essentially 
an electromagnet provided with a flat work face. Fig. 397 shows 
a magnetic chuck of the type commonly used on planers, milling 
machines, boring mills, and other machines producing plane sur¬ 
faces. Fig. 398 shows how the magnetic chuck is adapted to a rotat¬ 
ing spindle. Each of these tools are of the greatest service in machin¬ 
ing small and rather thin pieces, as magnetic holding leaves the work 
surface clear for tooling. 

The magnetic chuck shown in Fig. 397 is really two standard 


353 





































340 


MACHINE SHOP WORK 



style 10-inch X 32-inch Heald magnetic chucks, butted together 
end to end, used on a surface grinding machine. In the illustration 


528 cones are in position. Time for placing does not exceed twelve 
minutes. The cones are end ground to a limit of 0.002 inch. 


354 


Courtesy of Heald Machine Company, Worcester, Massachusetts 





MACHINE SHOP WORK 


341 


The total time for the job from start to finish is If hours. 
Such a job illustrates the usefulness of the magnetic chuck upon 
a surface grinding machine. The results are similar when used 
upon the milling machine and for certain planer work. 



Fig. 398. Heald Internal Grinder Fitted with Magnetic Chuck 
Courtesy of Heald Machine Company, Worcester, Massachusetts 

Fig. 398 shows the possibilities of a rotary magnetic chuck 
used in the grinding of holes, while Fig. 399 is illustrative of its 
use in lathe work. The essential quality of magnetic chucks is that 
the holding power is exerted upon the work without material straps, 
bolts, or other devices, which of themselves take up space and may 


355 








342 MACHINE SHOP WORK 



Fig. 399. Close View of Heald Chuck Holding Disc for Tuning Operation 

interfere with the tooling which needs to be accomplished. Also 
they are instantaneously discharged by pulling a simple switch. 



Fig. 400. View of Magnetic Chuck Casting 
and Unit Coils 

Courtesy of Heald Machine Company, 

Worcester, Massachusetts 

The diagram, Fig. 400, illustrates the simple construction of 
the magnetic chuck. 


356 









MACHINE SHOP WORK 


343 



Fig. 401. Heald Magnetic Chuck Faceplate 


SAFETY FIRST 

A growing apprehension of the possibilities of so safeguarding 
machines that the operator is reasonably sure that he incurs little 
risk of life or limb, would seem to render timely a few words on this 
subject. 

Safety Devices on Machines. It is well perhaps to note that no 
machine can be absolutely safeguarded and be operative. The 
danger to the operator can, however, with care, be reduced to a 
minimum, and much is now being done to safeguard such portions 
of machine tools as the gearing, the clutches, clutch couplings, 
belts, set screws, etc. 

While the whole subject of “safety first” includes the building 
in which the machines are located, as well as the machines themselves, 
in general the machines should receive the first consideration. It 
is the truth that nothing can safeguard a machine against ignorance, 
bravado, or heedlessness on the part of the operative, and he must 
either educate himself or be educated to a point where he will vol¬ 
untarily endeavor to protect himself against injury. 

While it is usually true that the employe has very little direct 
authority in the matter of providing safeguards for the machines 
at which he may work, also in regard to the building in which he 
works, he may, by means of tactful suggestions made to the proper 
person, do much indirectly to promote the cause of safety. While 
usually the building in which the machinery is located must be 
taken as it is, many improvements can be made with safety first 
in view. 


357 




344 


MACHINE SHOP WORK 


Means of Safeguarding. Fire Hazard. One of the common 
hazards is the danger of fire. This is a real danger to the employes' 
life if the building exceeds the height of a single story; and properly 
guarded stairways and fire escapes should provide easy exit. All 
exits should be designated by the word EXIT in prominent char¬ 
acters and all doors should open outward. Unobstructed passage 
to any and all exits should be maintained at all times, and all stair¬ 
ways should preferably be of a generous width and without bends 
or crooks. All stairways or other floor openings, as for example, 
elevator wells, should be safeguarded by suitable railings or nettings. 

Power Transmission. The transmission of power by means 
of shafting, pulleys, and belting, is a prominent hazard to safety 
unless it is properly safeguarded. Power driven gears, pulleys, 
and flywheels should be encased to at least 6 feet from the floor. 
All chain drives should be entirely encased, as should trains of 
gearing. Belts should be guarded to a height of at least 6 feet 
from the floor or any adjacent platform. 

Shafting. All line shafting, even if, as is usually the case, 
it is suspended from the ceiling, should be provided with necessary 
safeguards, as for example, smooth couplings, flush set screws, 
proper provision for belts when not on the pulleys, etc. 

Electrical Transmission. All switchboards should stand out 
from the wall to have a free and clear space sufficient for easy and 
safe inspection. This space should be enclosed with provision for 
padlocked entrances and exits. It should have also a prominent 
sign DANGER. 

Wherever it is possible for the operative to accidentally make 
a dangerous ground connection, rubber matting should be provided 
and kept in a dry condition. High voltage lines should have prom¬ 
inently attached red signs stating the voltage. All switches should 
be guarded from accidental contacts. 

Machinery. All those machines which receive their power 
through a system of gearing, screws, spindles, pulleys* etc., should 
have all the working mechanisms covered. It will be noted that in 
essentially all of the production machines shown in this course, 
all moving parts have been encased wherever it was possible to 
do so without interfering with the convenient operation of the 
machine. 


358 


MACHINE SHOP WORK 


345 


Woodworking Machinery. This is a very dangerous class of 
machinery and should receive special care in providing guards. 
The floor adjacent to such machinery as this should, as in the case 
of electrical apparatus, be covered with rubber matting. 

Grinding Machines. Owing to the high rotative speed given to 
abrasive wheels in modern grinding, especial precautions should 
also be made to safeguard the workmen from a possible wheel 
explosion. While the manufacturer is painstaking in his efforts 
to safeguard his machines, it is not possible for him to prevent 
an ignorant or careless operative from rendering such safeguards 
inoperative. 

Use of Goggles. In all operations which result in flying chips, 
the use of goggles is recommended. This includes such operations 
as snagging, chipping, hand grinding, and many other jobs. 

Press Work. All machines for punching, shearing, or pressing 
metals or other materials should, in addition to the ordinary safe¬ 
guards, be provided with special safeguards at the working opening. 
These should absolutely prevent the closing of the machine while 
the operatives’ hands are exposed to injury. 

In General. The art of safeguarding the workman is one that 
requires thought, ingenuity, and an unwillingness to ignore any 
little detail that will in any way achieve the end sought —Safety First. 


359 

















































. 



































• < 














































































































































































































































































REVIEW QUESTIONS 


















review questions 

ON THE SUBJECT OF 

MACHINE SHOP WORK 

PART I 


1. A micrometer caliper shows a reading of .463; how many 
times must the thimble be turned to produce a reading of .587? 
(Assume 40 threads per inch.) 

2. Discuss measurement of wire. 

3. What is a soft hammer, and when is it used? 

4. What is a chuck drill? 

5. What methods are used for cleaning a file? 

6. How should a file be held for fine filing? 

7. Describe the surface gage. 

8. Describe the micrometer caliper. 

9. Describe two common forms of chisel, and state under 
what conditions they are used. 

10. Why is not the cutting surface of a file perfectly flat? 

11. What methods are used for holding a file for filing large 
surfaces? 

12. Describe the twist drill. 

13. What is a vernier? 

14. What is the result when the lips of the twist drill are of 
unequal length? 

15. When are reamers used? 

16. How much less should the diameter of the drilled hole be 
than finish size if a reamer is to be used? 

17. Explain the methods of cutting screw threads with a die. 


363 




REVIEW QUESTIONS 


ON THE SUBJECT OF 

MACHINE SHOP WORK 

PART II 


1. What is a mandrel? 

2. Describe the rise-and-fall rest. 

3. How long will it take to turn a chip 18 inches on a shaft 
24 inches long and 3J inches in diameter? 

Assume cutting speed 20 feet per minute. 

Assume feed 5V inch per revolution. 

4. Describe the process of making a taper fit. 

5. The lead screw has a pitch of \ inch. What is the ratio 
of gears to be used to cut a screw with 18 threads per inch? 

6. Describe the process of bringing the countersink back 
to center. 

7. For what purpose is the back gear of a lathe? 

8. Describe some method of adjusting pieces to center. 

9. Describe the shapes, and state the uses of the following 
lathe tools: Diamond point, side or facing tool, parting tool, and 
square-nosed tool. 

10. Why are lubricants used in turning? 

11. Describe the method for finding the clearance for a tool 
for cutting square threads. 

12. On account of not having the proper gears at hand, 
compound gears must be used. The lead screw has 4 threads 
per inch, and a screw having 9 threads per inch is to be cut. The 
gears chosen for drivers are of 24 teeth on the spindle gear and 
30 on the intermediate. What gear should be used for the inter¬ 
mediate driven if the screw gear has 60 teeth? 

13. Why should a boring tool have more clearance than a 
turning tool? Explain with sketch. 

14. Explain the method of turning a taper by setting the 
tailstock over. 

15. In what direction does the carriage run when cutting a 
right-hand thread? 


364 



REVIEW QUESTIONS 

ON THE SUBJECT OF 

MACHINE SHOP WORK 

PART III 


1. What is interchangeable work? 

2. Explain the method of grinding valves. 

3. What is pickling? 

4. In what direction relative to the motion of the cutter 
should the work on a milling machine be fed? 

5. What is the difference between peening and bending? 

6. What is the difference in the rates of revolution given 
for surface milling of cast iron, with a surface milling cutter 3J 
inches in diameter, according to Addy’s rule and the Brown 
and Sharpe table? 

7. What are the principal uses of the grinding machine? 

8. What is a surface plate? Describe the process of making. 

9. Describe the hydrostatic level. 

10. What is the safe rate of revolution of an emery wheel 5 
inches in diameter, if its surface speed is not to exceed 4,000 feet 
per minute? 

11. A surface of cast iron is to be finished in one cut on the 
milling machine. The casting is 8 inches long and 5 inches wide. 
The milling cutter has a diameter of 3 inches and a width of 2 
inches. How long will it take to do the work? Assume feed of 
2 \ inches. 

12. What is a lap? Of what metal should it be made? 

13. How may a permanent joint be made? 

14. Describe in a general way the setting of a machine. 


365 



REVIEW QUESTIONS 


ON THE SUBJECT OF 

MACHINE SHOP WORK 

PART IV 


1. Describe a spur gear. 

2. What is the difference between the circular pitch and the 
pitch circle? 

3. What is the diametral pitch? 

4. How do you determine the ratio of two gears when the 
numbers of teeth are given? 

5. How is the involute curve laid out? 

6. What is a bevel gear? 

7. Having the diameter and the diametral pitch given, how 
do you find the number of teeth? 

8. Describe a worm and worm gear. 

9. What is a hob, and for what purpose is it used? 

10. What is a spiral gear? 

11. What are meant by the’lead and the pitch of a spiral gear? 

12. What are the two processes for cutting gear teeth? 

13. Why is it difficult to cut correctly shaped bevel gear teeth 
with a revolving cutter? 

14. What is the difference between a Fellows gear shaper and 
a Gleason gear planer? 

15. What is a turret lathe? 

16. What is the object of a turret lathe? 

17. How many classes of turret lathes are there? What are 
they? 

18. What is an automatic turret lathe? 

19. How is the turret revolved in an automatic machine? 

20. What is a box tool? What is it used for? 

21. What is a forming tool? 


366 



REVIEW QUESTIONS 

ON THE SUBJECT OF 

MACHINE SHOP WORK 

PART V 


1. Describe the construction methods in machine building. 

2. What is meant by “types of workmen”? 

3. What are some of the fundamental principles in jig 
design? 

4. How is “direct driving” accomplished in machine shops? 

5. What points have to be considered in the selection of 
an abrasive wheel? 

6. Describe the process of internal cylindrical grinding. 

7. Name the different types of milling machines. 

8. What types of drilling machines are there, and for what 
class of work are they designed? 

9. Name and describe the general types of turning lathes. 

10. For what class of work are automatics used? 

11. What is meant by broaching? 

12. Explain fully the difference between tool steel and high¬ 
speed steel. 

13. What kind of lubricant is used in heavy machining? 

14. Explain the difference between a jig and a fixture. 

15. What can you say in regard to “safeguarding” in 
machine shop practice. 

16. For what purposes is a magnetic chuck used? 

17. Name and describe the different types of ball bearings. 

18. What is meant by “spotting”? 

19. What are jig buttons and where are they used? 


367 



MACHINE SHOP WORK 


20. What are limits and how are such limits specified? 

21. How is production work increased in a planing machine? 

22. What system of lubrication is used in automatics? 

23. How are cutting feeds determined? 

24. What is flat surface grinding? 

25. Describe some of the grinding methods. 

26. What is a wheel traverse? 

27. What comes under the head of heat treatment? 

28. What are bearing points in drill jigs? 

29. For what purpose is a “Lo-Swing” type of turning lathe 
used? 

30. What is automatic control in production machines? 

31. What feed is generally given to a light high-speed driller? 

32. What feed may be given to a heavy high-speed driller? 

33. What determines the cutting speed in a milling machine? 

34. What is a boring fixture? 


368 


INDEX 


369 




INDEX 


The page numbers of this volume will be found at the bottom of the pages; 
the numbers at the top refer only to the section . 


Page 


Page 

A 


Calipers (continued) 

Angle cutters 

151 

outside and inside 

19 

Automatic gear-cutting machine 

236 

transfer 

21 

Automatic screw machines 

262 

vernier 

26 

hollow mills 

274 

Cams 

178 

setting-up machine 

274 

Cape chisel 

35 

types of 

263 

Carpenter’s rule 

17 

Automatic turning and chucking 


Center punch 

46 

machine 

264 

Center square 

16 

Automatics 

317 

Chisels 

35 



cape 

35 

B 


chipping 

37 

Ball bearings 

349 

cutting edge of 

36 

load capacities 

350 

diamond-point 

36 

lubrication 

350 

flat 

35 

types of 

350 

round-nose 

36 

use of 

349 

Cleveland automatic machine 

266 

Becker gear-cutting machine 

236 

Cold chisels 

199 

Belting 

202 

Combination set 

16 

Bench gear-cutting machine 

237 

Cutter arbor 

147 

Bench miller 

157 

cutter, locating position of 

148 

Bevel 

15 

fastening cutter in arbor 

147 

Bevel gears 

218 

Cutting speeds 

168 

Bilgram gear-planing machine 

239 

Cutting speeds and feeds 

317 

Bolt cutter 

62 

Cutting tools 

35 

Bolt threads, cutting of 

61 

chisels 

35 

Boring fixtures 

348 

files 

38 

Broaching machines 

323 

hand scraping 

45 

types of and nature of work 

323 

Cutters, lubrication of 

233 

Brown and Sharpe automatic screw 


Cutters, speed of 

233 

machine 

270 

D 


Brown and Sharpe gear-cutting 



machine 

235 

Diamond-point chisel 

36 



Die holders, threading of 

61 

C 


Dividers 

18 

Caliper square 

22 

Dovetails 

175 

Calipers 

19 

Drillers 

121 

caliper square 

22 

drilling operation 

121 


Note.—For page numbers see foot of pages. 


371 



2 


INDEX 



Page 


Page 

Drillers (continued) 


F 


flat 

121 

Farmer drills 

50 

heavy high-speed 

304 

Feed 

233 

holding work 

128 

Fellows gear shaper 

237 

laying out 

127 

Files 

38 

light high-speed 

305 

characteristics 

38 

multiple spindles 

125 

choice of 

42 

power feed 

123 

cleaning 

42 

radial 

125 

convexity of 

39 

sensitive 

122 

correct filing position 

41 

special 

305 

draw filing 

43 

tapping 

130 

handles 

41 

Drilling 

48 

height of work for 

40 

Drilling machines 

304 

polishing 

43 

automatics 

317 

style and cuts 

38 

cutting speeds and feeds 

317 

use of powders and cloths 

44 

heavy high-speed drillers 

304 

Filing templets 

48 

holding work 

307 

Fitting 

194 

light high-speed drillers 

305 

Fitting brasses 

197 

lubrication 

308, 317 

Fixed gages 

28 

production figures 

306 

Flat chisel 

35 

special drillers 

305 

Flat chucking reamer 

54 

turning lathe 

310 

Flat drills 

48, 121 

Drilling operation 

121 

Flat square 

14 

Drills 

48 

Fluting rollers 

199 

care of 

51 

Fluting taps and reamers 

176 

lubrication 

51 

Form cutters 

152 

resharpening 

52 



speed of 

51 

G 


farmer 

50 

Gages 


flat 

48 

fixed 

28 

flat chucking drill 

48 

limit 

30 

twist 

48 

plug 

29 

tapered shanks 

49 

ring 

29 

Duplex milling machines 

164 

Gang mills 

151 



Gear cutting 

205 

E 


tooth parts, names of 

207 



toothed gearing, theory of 

205 

End mills cutter 

154 

Gear-cutting machines, types of 

234 

dovetail cutters 

154 

automatic 

236 

T-slot cutter 

154 

Becker 

236 

Engine lathes 

68, 245 

bench 

237 

gear drive 

69 

Bilgram gear-planing machine 

239 

handling work 

71 

Brown and Sharpe 

235 

tool-feeding mechanism 

71 

Fellows gear shaper 

237 

spindle arrangement 

69 

Gleason gear planer 

238 

Expanding reamer and arbor 

55 

Whiton 

234 


Note.—For page numbers see foot of pages. 


37 2 


INDEX 


3 


Page 

Gear-cutting processes 226 

cutters, lubrication of 233 

cutters, speed of 233 

feed 233 

gear teeth, tools for testing 230 

general conditions of 230 

hobbing gears 229 

milling process 226 

planing process 228 

spiral 233 

Gear teeth, tools for testing 230 

Gear-tooth curves, development of 209 
Gears 180 

bevel 183 

dividing head, use of 181 

forms of cutters 180 

rack cutting 183 

spiral 183 

worm 183 

Gears, designing 208 

bevel gears 218 

diametral pitch method 208 

fixed pitch method 208 

gear-tooth curves, development of 209 
internal gears 215 

spiral gears 223 

teeth racks 217 

worm gearing 220 

Gears (internal) 215 

Generating surface plates 196 

Gleason gear planer *238 

Graver 67 

Grinding machine 183, 284 

abrasive wheels 287 

cylindrical grinding 285 

features of 184 

finishing to size after caseharden¬ 
ing 185 

grinding allowances 287 

grinding methods 288 

grinding wheel, selecting 187 

lapping 188 

lubrication 187 

usefulness 284 

value of 183 

wheel speed 285 

wheel traverse 286 


Note.—For page numbers see foot of pages. 


Grinding valves 

Page 

196 

Grinding wheel 

187 

Guide bushing 

344 

H 

Hammers 

34 

soft 

35 

Hand-operated tools 

11 

cutting tools 

35 

drilling 

48 

drills 

48 

hammers 

34 

hand punches 

46 

hand threading tools 

57 

measuring tools 

11 

reamers 

53 

templets 

47 

Hand punches 

46 

center punch 

46 

prickpunch 

46 

scratch awl 

47 

Hand reaming 

54 

Hand scraping 

45 

scraping for finish only 

46 

testing plane surfaces 

45 

Hand tapping 

58 

starting tap 

59 

use of bottoming tap 

59 

Hand threading tools 

57 

hand tapping 

58 

lubrication 

59 

machine tapping 

59 

sizes of drill for tapped hole 

57 

taps, types of 

57 

threading dies 

60 

Hand turning, tools for 

66 

graver 

67 

round nose 

67 

slide rest 

68 

Hard metals, drilling of 

195 

Hobbing gears 

229 

Holes, laying out and drilling 

174 

Horizontal milling machines 

158, 299 

blacklash error, avoiding 

160 

micrometer graduations 

159 


373 


INDEX 


4 



Page 


Page 

I 


Measuring tools (continued) 


Inserted-tooth cutters 

151 

surface gage 

11 

1 A 

Interlocking cutters 

151 

try square 
linear measurement 

14 

16 

J 


calipers 

19 

Jigs 

48 

carpenter’s rule 

17 

Joints 

197 

dividers 

18 



fixed gages 

28 

K 


micrometers 

22 

Keyseat rule 

13 

steel rule 

17 

L 


•surface plates 

32 

Lapping * 

188 

work bench 

32 

Lathe, layout for 

193 

work vises 

33 

Lathes 

65 

Micrometers 

22 

engine lathes 

68 

reading of 

25 

origin 

65 

Milling cutters 

145 

speed 

65 

angle 

151 

tools for hand turning 

66 

care of 

166 

Limit gages 

30 

characteristics 

147 

Lining shafting 

200 

classification 

145 

Lubrication 59, 187, 

317, 323 

cutter arbor 

147 



end mills 

154 

M 


form 

152 

Machine building vs. machine manu- 

gang mills 

151 

facturing 

279 

grinding 

166 

construction methods 

279 

inserted-tooth 

151 

workmen, types of 

279 

interlocking 

151 

Machine setting 

201 

mounting, methods of 

155 

Machine shop work 

11-359 

plain 

149 

hand-operated tools 

11 

side 

149 

modern manufacturing 

279 

spiral 

149 

power-driven tools 

65 

Milling fixtures 

347 

shop suggestions 

194 

Milling machine vs. shaper and planer 143 

work, laying out 

190 

Milling machines 

143, 299 

Machine tapping 

59 

cutting feeds 

304 

Magnetic chucks 

353 

cutting speeds 

301 

uses in production work 

353 

horizontal 

299 

Marking templets 

47 

operations (simple) 

143 

Measuring tools 

11 

planer 

299 

angular measurement 

11 

production cutters 

300 

bevel 

15 

tool lubrication 

304 

center square 

16 

types of 

157 

combination set 

16 

bench miller 

157 

flat square 

14 

duplex 

164 

keyseat rule 

13 

horizontal 

158 

protractor 

16 

plain and universal 

millers, 

straightedge 

12 

distinction between 161 


Note.—For page numbers see foot of pages. 


374 


INDEX 


Page 

Milling machines (continued) 
types of 

planer type 162 

slabbing miller 159 

vertical 163 

vertical 299 

work holding 301 

Milling operations 165 

cams 178 

classification 165 

angle milling 166 

form milling 166 

plane milling or surface milling 165 
profiling 166 

side milling or face milling 165 

cutting speeds 168 

dovetails 175 

fluting taps and reamers 176 

grinding milling cutters 166 

holes, laying out and drilling 174 

milling cutters, care of 166 

milling machine, preparing of 168 

oil, use of on machines and work 173 
spirals 177 

splining shafts 175 

Milling process 226 

Modern manufacturing 279 

ball bearings 349 

machine building vs. machine 

manufacturing 279 

magnetic chucks 353 

production machines 283 

broaching machines 323 

drilling machines 304 

grinding machines 284 

milling machines 299 

planing machines 320 

production methods 280 

automatic control 281 

automatics 281 

ball bearings 282 

bearing alloys 282 

bearing lubrication 282 

cold worked metals 281 

cutting feeds 280 

cutting lubrication 280 

cutting speeds 280 


ftote.—For page numbers see foot of pages. 


5 

Page 


Modern manufacturing (continued) 
production methods 

die casting machine parts 281 

drives 282 

heat treatment 282 

jigs and fixtures 283 

motion study 283 

overheads 283 

selling costs 283 

special die forgings 282 

special molding processes 281 

specialized cutting steels 280 

single purpose machines 280 

time study 283 

production tools, jigs and fixtures 328 
safety first 357 

safeguarding, means of 358 

safety devices on machines 357 

Monitor lathe 244 

Multiple spindles 125 

N 

No. 2 automatic screw machine 274 

O 

Oil, use of on machines and work 173 

P 

Peening 194 

Pickling 199 

Pipe threads, cutting of 61 

Plain milling cutters 149 

Plain and universal millers, distinc¬ 
tion between 161 

Plain shell reamer 55 

Planer fixtures 348 

Planer milling machine 299 

Planer tools 133 

Planer type milling machines 162 

milling attachments for 162 

Planers 130 

plate 137 

tools 133 

work, holding 134 

Planing machines 320 

holding work 321 

lubrication 323 


375 


6 


INDEX 


Planing machines (continued) 
production planers 
Planing process 
Plate planer 
Plug gages 
Power-driven tools 

automatic screw machines 

drillers 

gear cutting 

gear-cutting machines, types of 

gear cutting processes 

gears, designing 

grinding machine 

lathe equipment 

lathe operations 

lathes 

milling cutters 
milling machines 
milling operations 
planers 
shapers 
turret lathes 
Power feed driller 
Prickpunch 
Production planers 
Protractor 

R 

Racks, teeth of 
Radial driller 
universal 
Reamers 
expanding 
hand reaming 
plain shell 

reamer with inserted blades 
rose shell 
solid hand 

spiral chucking reamer drill 
taper 
use of 
Ring gages 
Rose shell reamer 
Round bars, cutting of 
Round-nose chisel 

Note.—For page numbers see foot of 


s 

Page 

Scale 

199 

Scratch awl 

47 

Sensitive driller 

122 

Shapers 

138 

Side milling cutters 

149 

Slabbing miller 

159 

Slide rest 

68 

Splining shafts 

175 

Slotter 

140 

Solid dies 

60 

Solid hand reamer 

54 

Speed lathes 

65 

Spiral chucking reamer 

55 

Spiral cutters 

149 

Spiral gears 

223 

cutting of 

233 

Spirals 

177 

Split dies 

60 

Spotting 

346 

Steel rule 

17 

Straightedge 

12 

Surface gage 

11 

Surface plates 

32 

T 

Tables 



allowances for grinding 288 

bushings for holes reamed with 

rose chucking reamers 342 
carbon-steel drills 307 

data on rates of production with 
different types of 
broaching machines 324 
dimensions of lining bushings 340 
dimensions of removable drill 

bushings 341 

dimensions of stationary drill 

bushings 340 

drills, speed of 52 

end or face milling of cast iron 173 
face milling of soft machinery steel 173 
high-speed drills 307 

involute gear tooth parts 218 

load capacities of radial ball bear¬ 
ings 351, 352 

loads for thrust collar bearings 353 


Page 

320 

228 

137 

29 

65 

262 

121 

205 

234 

226 

208 

183 

72 

95 

65 

145 

143 

165 

130 

138 

241 

123 

46, 

320 

16 

217 

125 

126 

53 

55 

54 

55 

56 

55 

54 

55 

56 

53 

29 

55 

190 

36 

pages. 


376 


INDEX 


7 


Page 


Tables (continued) 

Norton grade list 290 

rate of grinding gun parts on ver¬ 
tical grinder 298 

revolutions per minute for various 

sizes of grinding 286 

selection of grades 292, 293 

speed of grinding wheels 188 

speeds and feeds for milling cutters 171 
surface milling of cast iron 172 

surface milling of soft machinery 

steel 172 

taps and corresponding drills 58 

U. S. standard threads, bolts and 

nuts 112 

Taper reamers 56 

types of 56 

Tapping 130 

Taps 57 

Templets 47 

filing 48 

jigs 48 

marking 47 

Threading dies 60 

bolt threads, cutting of 61 

pipe threads, cutting of 61 

solid dies 60 

split dies 60 

Tolerances 343 

Toothed gearing, theory of 205 

Try-square 14 

Turning lathe 310 


Note.—For page numbers see foot of pages. 


Page 

Turret-lathe tools 251 

box tool (double) 253 

box tool (simple) 253 

box tool holder 254 

cross-slide 255 

plain drill holder 252 

releasing holder 253 

split collet 252 

tool clamp 254 

turret holder 254 

Turret lathes 241 

classification of 242 

operations 256 

original form of 242 

tools 251 

Twist drills 48 

U 

Universal multiple-spindle automatic 

machine 268 

V 

Vertical milling machines 163, 299 

Vernier calipers 26 

how to read 27 

W 

Whiton gear-cutting machine 234 

Work bench * 32 

Work vises 33 

Worm gearing 220 


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